Wireless communication device

ABSTRACT

A wireless communication device for transmitting/receiving a high-frequency signal having a predetermined communication frequency. The wireless communication device includes an antenna pattern having an inductance component, an RFIC element connected electrically to the antenna pattern and a capacitive coupling portion capacitively coupling specific confronting regions facing each other of the antenna pattern at multiple points on the antenna pattern, to make up an LC parallel resonant circuit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication No. PCT/JP2018/016363, with an international filing date ofApr. 20, 2018, which claims priority of Japanese Patent Application No.2017-083957 filed on Apr. 20, 2017, Japanese Patent Application No.2017-203663 filed on Oct. 20, 2017, and Japanese Patent Application No.2018-009946 filed on Jan. 24, 2018, the entire contents of each of theapplications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a wireless communication device havingan antenna and, more particularly, by induction field or radio wave, toa wireless communication device utilizing a radio frequencyidentification (RFID) technology performing short-range communicationfor non-contact reading and writing of semiconductor memory data.

BACKGROUND

It is conceived to automate merchandise accounting by attaching an “RFIDtag” that is a wireless communication device to a commodity. Accordingto this automated settlement system, when a basket containing goods withthe “RFID tag” is placed on a checkout counter, information from the“RFID tag” is read to display a commodity price.

A wide variety of commodities are dealt in stores such as supermarketsand some of foodstuffs as commodities may be warmed up immediately afterthe purchase thereof so that the purchaser can eat and drink on thespot. Examples of commodities warmed up to eat and drink are foodstuffssuch as a lunchbox and a cup noodle. These commodities are considered tobe heated up using an electromagnetic wave heating apparatus, i.e. aso-called “microwave oven” at the stores.

In the “RFID tag”, a radio-frequency integrated circuit (RFIC) chip anda metal material such as an antenna pattern that is a metal film areformed on a paper material or a resin material. Therefore, in the casewhere with such an “RFID tag” attached to a commodity, the commodity isheated up by the “microwave oven”, for example, in the case where alunchbox with the “RFID tag” is heated up, electromagnetic waves fromthe “microwave oven” are absorbed in not only the lunchbox but also the“RFID tag” so that the metal material portions are subjected toconcentration of electric fields and discharge with eddy current flowingthrough the metal material, whereupon the metal itself may be heated upand sublimate or the paper material or the resin material forming thetag may ignite, resulting in a risk of ignition of the “RFID tag”.

For the purpose of reducing the risk of ignition in the “RFID tag” asdescribed above, a configuration of “flame-retardant tag” has beenproposed (see Patent Document 1).

Patent Document 1: Japanese Laid-Open Patent Publication No.2006-338563.

In the “flame-retardant tag” disclosed in Patent Document 1, a substratemounted with an IC chip and the antenna pattern is made of aflame-retardant material. Hence, due to the flame-retardant material,the substrate itself is extinguished in several seconds or several tensof seconds after ignition, but the metal material portions formed on thesubstrate have a high possibility to continuously discharge, notproviding a configuration capable of securely preventing the risk ofignition of the substrate and the potential to ignite the goods.

SUMMARY OF THE INVENTION

It is an object of the present disclosure to provide a wirelesscommunication device configured to prevent the risk of ignition in anarticle having the wireless communication device attached thereto eventhough the article with the wireless communication device is irradiatedwith an electromagnetic wave in a higher frequency band than apredetermined communication frequency.

Thus, a wireless communication device of an exemplary aspect isdisclosed the includes an antenna pattern having an inductancecomponent; an RFIC element connected electrically to the antennapattern; and a capacitive coupling portion capacitively couplingspecific confronting regions facing each other of the antenna pattern ata plurality of points on the antenna pattern, to make up an LC parallelresonant circuit.

According to the present disclosure, a wireless communication device canbe provided that is configured to preventing the risk of ignition in anarticle with the wireless communication device even though the articleis irradiated with an electromagnetic wave in a higher frequency bandthan a predetermined communication.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view showing a wireless communication device (RFID tag)of a first embodiment.

FIG. 2A is a diagram showing a front surface (first main surface) of anantenna substrate in the wireless communication device of the firstembodiment.

FIG. 2B is a diagram showing a back surface (second main surface) of theantenna substrate in the wireless communication device of the firstembodiment.

FIG. 3A is a diagram showing an exemplification of the wirelesscommunication device of the first embodiment attached to an article.

FIG. 3B is a diagram showing an exemplification of the wirelesscommunication device of the first embodiment attached to an article.

FIG. 4 is an exploded perspective view showing an RFIC package in thewireless communication device of the first embodiment.

FIG. 5 is a diagram schematically showing, in the form of circuitdiagram symbols, a capacitive coupling portion for an antenna pattern inthe wireless communication device of the first embodiment.

FIG. 6 is a pseudo-equivalent circuit showing a partial configuration ofa plurality of LC parallel resonant circuits in the wirelesscommunication device of the first embodiment.

FIG. 7 is an equivalent circuit diagram showing an overall configurationexample of the plurality of LC parallel resonant circuits in thewireless communication device of the first embodiment.

FIG. 8 is a frequency characteristic diagram showing the result ofsimulation experiments in the wireless communication device of the firstembodiment.

FIG. 9 is a Smith chart of the simulation experiments on the wirelesscommunication device of the first embodiment.

FIG. 10A is a diagram showing how current flows when receiving a signalof a UHF-band communication frequency (920 MHz) in the wirelesscommunication device of the first embodiment.

FIG. 10B is a diagram showing how current flows when receiving a signalof a heating frequency (2.4 GHz) used in an electromagnetic wave heatingapparatus (“microwave oven”) in the wireless communication device of thefirst embodiment.

FIG. 11 is a diagram showing the direction in which current tries toflow when the antenna pattern and the capacitive coupling portion(line-to-line capacitance pattern) receive a signal having the heatingfrequency in the wireless communication device of the first embodiment.

FIG. 12A is a diagram showing gains for all directions related to thewireless communication device of the first embodiment.

FIG. 12B is a diagram showing the gain of the wireless communicationdevice of the first embodiment.

FIG. 13 is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a second embodiment.

FIG. 14 is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a third embodiment.

FIG. 15 is a plan view showing a variant of the wireless communicationdevice of the third embodiment.

FIG. 16A is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a fourth embodiment.

FIG. 16B is an equivalent circuit diagram showing a configuration of theantenna pattern in the wireless communication device of the fourthembodiment.

FIG. 17A is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a fifth embodiment.

FIG. 17B is an equivalent circuit diagram showing a configuration of theantenna pattern in the wireless communication device of the fifthembodiment.

FIG. 18 is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a sixth embodiment.

FIG. 19A is a plan view showing the configuration of the wirelesscommunication device (RFID tag) of the sixth embodiment.

FIG. 19B is an equivalent circuit diagram of a partial configuration ofthe antenna pattern in the wireless communication device of the sixthembodiment.

FIG. 19C is an explanatory view showing current flowing through a partof the antenna pattern in the wireless communication device of the sixthembodiment.

FIG. 20 is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a seventh embodiment.

FIG. 21 is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of an eighth embodiment.

FIG. 22 is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a ninth embodiment.

FIG. 23 is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a tenth embodiment.

FIG. 24 is an exploded perspective view showing a configuration of awireless communication device (RFID tag) of an eleventh embodiment.

FIG. 25 is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a twelfth embodiment.

FIG. 26 is a plan view of the wireless communication device (RFID tag)of the twelfth embodiment when attached to an article.

FIG. 27 is a diagram showing an exemplification of the wirelesscommunication device of the twelfth embodiment attached to an article.

FIG. 28 is a frequency characteristic diagram showing the result ofsimulation experiments in the wireless communication device of the sixthembodiment.

FIG. 29 is a Smith chart of the simulation experiments on the wirelesscommunication device of the sixth embodiment.

FIG. 30A is a diagram showing how current flows when receiving a signalof a UHF-band communication frequency (920 MHz) in the wirelesscommunication device of the sixth embodiment.

FIG. 30B is a diagram showing how current flows when receiving a signalof a heating frequency (2.4 GHz) used in an electromagnetic wave heatingapparatus (“microwave oven”) in the wireless communication device of thesixth embodiment.

FIG. 31A is a diagram showing gains for all directions related to thewireless communication device of the sixth embodiment.

FIG. 31B is a diagram showing gains on an XZ plane of FIG. 12A, relatedto the wireless communication device of the sixth embodiment.

FIG. 32 is a plan view showing a configuration of a wirelesscommunication device (RFID tag) of a thirteenth embodiment.

FIG. 33 is a plan view showing a variant of the wireless communicationdevice of the thirteenth embodiment.

FIG. 34A is a plan view of a wireless communication device (RFID tag) ofa fourteenth embodiment when attached to an article.

FIG. 34B is an equivalent circuit diagram showing an antenna patternconfiguration in the wireless communication device of the fourteenthembodiment.

FIG. 35A is a plan view of a wireless communication device (RFID tag) ofa fifteenth embodiment when attached to an article.

FIG. 35B is an equivalent circuit diagram showing an antenna patternconfiguration in the wireless communication device of the fifteenthembodiment.

FIG. 36 is a plan view showing a wireless communication device (RFIDtag) of a sixteenth embodiment.

DETAILED DESCRIPTION

As an initial mater, it is noted that configurations of variousexemplary aspects of a wireless communication device according to thepresent disclosure will be described below.

Specifically, a wireless communication device of a first exemplaryaspect is provided for transmitting/receiving a high-frequency signalhaving a predetermined communication frequency. In this aspect, thedevice includes an antenna pattern having an inductance component; anRFIC element connected electrically to the antenna pattern; and acapacitive coupling portion capacitively coupling specific confrontingregions facing each other of the antenna pattern at a plurality ofpoints on the antenna pattern, to make up an LC parallel resonantcircuit.

Advantageously, the configured wireless communication device of thefirst exemplary aspect can suppress the occurrence of discharge in thewireless communication device even when a commodity with the wirelesscommunication device is irradiated with an electromagnetic wave in theband of higher frequencies than the communication frequency, therebymaking it possible to prevent the risk of ignition in the commodity withthe wireless communication device.

In the exemplary aspect, the antenna pattern may be of either arectilinear shape or a curvilinear shape. In a continuous antennapattern having pairs of confronting regions, the antenna pattern on onehand may lie in a direction intersecting the direction in which theantenna pattern on the other extends. Accordingly, each pair ofconfronting regions lying on the continuous antenna pattern may includethe case of parallel relationship to each other and the case of tilt ofeither one, and further include the case where curves confront eachother.

In the wireless communication device of a second exemplary aspect, theantenna pattern may be in the form of a meander having a plurality ofturn portions, and the capacitive coupling portion making up the LCparallel resonant circuit may be configured to capacitively coupleadjacent turn portions of the antenna pattern.

In the wireless communication device of a third exemplary aspect, theantenna pattern may be disposed on one surface of an antenna substratemade of a dielectric, and the capacitive coupling portion may bedisposed on the other surface of the antenna substrate.

In the wireless communication device of a fourth exemplary aspect, theantenna pattern and the capacitive coupling portion may be disposed onone surface of an antenna substrate, and the capacitive coupling portionmay be a conductor plate disposed between the specific confrontingportions facing each other.

In the wireless communication device of a fifth exemplary aspect, theantenna pattern and the capacitive coupling portion may be laminated viaa dielectric on one surface of the antenna substrate.

In the wireless communication device of a sixth exemplary aspect, theline length of the LC parallel resonant circuit may be formed shorterthan ½ wavelength of the predetermined communication frequency.

In the wireless communication device of a seventh exemplary aspect, theline length of the LC parallel resonant circuit may be formed shorterthan ½ wavelength of a frequency used in electromagnetic wave heating.

In the wireless communication device of an eighth exemplary aspect, theLC parallel resonant circuit may use as a resonant frequency a frequencyhigher than the predetermined communication frequency.

In the wireless communication device of a ninth exemplary aspect, the LCparallel resonant circuit may use as the resonant frequency a frequencyused in electromagnetic wave heating.

In the wireless communication device of a tenth exemplary aspect, the LCparallel resonant circuit may use as the resonant frequency a frequencyof a band of 2.4 to 2.5 GHz that is a frequency band used inelectromagnetic wave heating.

In the wireless communication device of an eleventh exemplary aspect,the antenna pattern may have a line width narrower than the line widthof the capacitive coupling portion.

In the wireless communication device of a twelfth exemplary aspect, theantenna pattern may be in the form of a meander having a plurality ofturn portions, and in an amplitude direction of the meander, the lengthof the antenna pattern may be longer than the length of the capacitivecoupling portion.

The wireless communication device of a thirteenth exemplary aspect maycomprise a resin antenna substrate having the antenna pattern formedthereon.

The wireless communication device of a fourteenth exemplary aspect maycomprise a film stuck on the resin antenna substrate, the film having aheat resistance higher than that of the antenna substrate.

In the wireless communication device of a fifteenth exemplary aspect,the antenna pattern may be configured from a dipole antenna having twodipole elements, and the capacitive coupling portion making up the LCparallel resonant circuit may be disposed on each of the dipoleelements.

In the wireless communication device of a sixteenth exemplary aspect, apart of a current path of the antenna pattern making up the LC parallelresonant circuit may be formed slimmer than the other portions on thecurrent path.

In the wireless communication device of a seventeenth exemplary aspect,a part of a current path of the antenna pattern making up the LCparallel resonant circuit may be formed thinner than the other portionson the current path.

In the wireless communication device of an eighteenth exemplary aspect,the antenna pattern may be configured to use a communication frequencyin a UHF band.

In the wireless communication device of a nineteenth exemplary aspect,the antenna pattern may be configured to use a communication frequencyin an HF band.

In the wireless communication device of a twentieth exemplary aspect,the resonant frequency by the antenna pattern in the absence of thecapacitive coupling portion may be higher than the communicationfrequency.

A wireless communication device of a twenty-first exemplary aspect is awireless communication device for transmitting/receiving ahigh-frequency signal having a communication frequency. In this aspect,the wireless communication device includes an antenna pattern havingconfronting regions facing each other; an RFIC element connectedelectrically to the antenna pattern; and a looped conductor patternarranged between each pair of the confronting regions of the antennapattern, the circumference of the conductor pattern being smaller than ½wavelength of the communication frequency.

In the wireless communication device of the twenty-first exemplaryaspect as configured in this manner, when the commodity with thewireless communication device is irradiated with an electromagnetic wavein the band of higher frequencies than the communication frequency, thelooped conductor pattern acts as an magnetic field antenna to generate amagnetic field. This allows the magnetic field antenna to be formed at aposition proximal to the antenna pattern receiving the electromagneticwave in the band of higher frequencies than the communication frequency.This degrades the antenna radiation efficiency in the frequency bandhigher than the communication frequency, enabling the energy received bythe antenna pattern to be reduced. In consequence, the risk of ignitionin the commodity with the wireless communication device can beprevented.

In the wireless communication device of a twenty-second exemplaryaspect, the antenna pattern may be in the form of a meander, and eachpair of the confronting regions of the antenna pattern may haverectilinear portions parallel to each other.

In the wireless communication device of a twenty-third exemplary aspect,the conductor pattern may be disposed between each pair of adjacent turnportions of the antenna pattern.

In the wireless communication device of a twenty-fourth exemplaryaspect, the conductor pattern may have a longitudinal direction and alateral direction, and the length of the conductor pattern in thelongitudinal direction may be formed into ¼ wavelength or less of thefrequency used in electromagnetic wave heating.

In the wireless communication device of a twenty-fifth exemplary aspect,a plurality of the conductor patterns may be arranged spaced apart fromeach other between respective pairs of the confronting regions of theantenna pattern.

In the wireless communication device of a twenty-sixth exemplary aspect,when the antenna pattern is irradiated with an electromagnetic wave of ahigher frequency than the communication frequency, a potentialdifference may increase between respective pairs of the confrontingregions of the antenna pattern between the plurality of conductorpatterns.

In the wireless communication device of a twenty-seventh exemplaryaspect, the conductor patterns having different circumferences may bearranged along rectilinear portions of the antenna pattern.

In the wireless communication device of a twenty-eighth exemplaryaspect, a first resonant frequency by the conductor pattern and a partof the antenna pattern including the confronting regions sandwiching theconductor pattern therebetween differs from a second resonant frequencyby the other conductor pattern and another part of the antenna patternincluding confronting regions sandwiching therebetween the otherconductor arranged next to the conductor pattern.

In the wireless communication device of a twenty-ninth exemplary aspect,the first resonant frequency may be a frequency used in electromagneticwave heating.

In the wireless communication device of a thirtieth exemplary aspect,the first resonant frequency may be a frequency of a zone of 2.4 GHz oremore and 2.5 GHz or less that is a frequency band used inelectromagnetic wave heating.

In the wireless communication device of a thirty-first exemplary aspect,a difference between a circumference of the conductor pattern and ½wavelength of the first resonant frequency higher than the communicationfrequency may be smaller than a difference between the circumference ofthe conductor pattern and ½ wavelength of the communication frequency.

In convenience stores and supermarkets selling goods to which a wirelesscommunication device is attached, a wide variety of goods such as foodsand daily commodities are dealt in. Of recent years, for the conveniencestores, various experiments have been carried out toward the practicaluse of “unmanned convenience store” which automates accounting for itemspurchased and bagging.

In order to automate accounting of goods at “unmanned conveniencestore”, it is envisaged that “RFID tag” as a wireless communicationdevice is attached to all the goods. The system is such that when ashopping basket holding goods with “RFID tag” is placed on a checkoutstand at “unmanned convenience store”, information from “RFID tag” isread for display of a purchase price. The purchaser puts cash or insertsa credit card for purchase price at a predetermined position to finishthe payment, and thereafter receives the goods automatically packed in ashopping bag, whereby purchase of goods at “unmanned convenience store”can be completed.

Exemplary embodiments as specific exemplifications of a wirelesscommunication device according to the present disclosure will now bedescribed with reference to the accompanying drawings. Although a lunchbox is described as an exemplification of an item to which “RFID tag”i.e. a wireless communication device of the following embodiments isattached, the item having the wireless communication device according tothe exemplary aspect attached thereto can be all of items handled inshops such as so-called “convenience stores”. The exemplary embodimentsrelate to a goods sales system in which the wireless communicationdevice having the same configuration is attached to all goods.

Although a microwave heating apparatus described in the embodimentsbelow is described as a so-called “microwave oven” performing dielectricheating, the microwave heating apparatus of the present disclosure is aheating apparatus having a dielectric heating function.

First Embodiment

FIG. 1 is a plan view showing a RFID tag 1 that is a wirelesscommunication device of a first exemplary embodiment. The RFID tag 1 isconfigured for wireless communication (transmission/reception) using ahigh-frequency signal with a UHF-band communication frequency (carrierfrequency) and can provide wireless communication in a wide frequencyband. As used herein, the UHF band means a frequency band of 860 MHz to960 MHz. The UHF-band communication frequency is an example of “firstfrequency for communication” in the present disclosure. As shown, theRFID tag 1 includes an RFIC package 2 described later, an antennapattern 3, a line-to-line capacitance pattern 4 as a capacitive couplingportion, and an antenna substrate 5 of dielectric. In the RFID tag 1 ofthe first embodiment, the antenna substrate 5 is made of aflame-retardant film having a flexibility and is of a substantiallyrectangular shape. If the antenna substrate 5 is not made of aflame-retardant film material, the film thickness of the antennasubstrate 5 may be 38 μm or less. As a result, the antenna substrate 5melts and deforms before combustion and therefore cannot keep its baseshape. The antenna pattern 3 has a line width of 100 μm to 300 μm and,if 150 μm or less, it can easily be disconnected simultaneously withdeformation of the antenna substrate 5. The antenna substrate 5 has onits front surface (i.e., the first main surface) the antenna pattern 3created by a film of a conductive material, such as aluminum foil orcopper foil. The antenna pattern 3 formed on the front surface (firstmain surface) of the antenna substrate 5 is mounted with the RFICpackage 2 such that the RFIC package 2 and the antenna pattern 3 areelectrically connected to each other. The electrical connection meansthat the two are connected to or coupled with each other such that ahigh-frequency signal is transmitted to allow operation, and is notlimited to DC connection.

The flame-retardant film material used as the antenna substrate 5 in thefirst embodiment can be a film of a resin material such as polyethylenetelephthalate (PET) resin or polyphenylene sulfide (PPS) resin to whicha halogen-based flame-retardant material is added or a flame-retardantcoating material is applied. The material of the antenna substrate 5 maybe a high-performance resin material such as polyethylene naphthalate(PEN) having a heat resistance. Furthermore, heat-resistant materialfilm may be applied to the dielectric antenna substrate 5 so as tofurther enhance the heat resistance as the antenna substrate 5 betweenthe antenna pattern 3 and the line-to-line capacitance pattern 4.

On the other hand, the antenna substrate 5 has on its back surface(second main surface) the line-to-line capacitance pattern 4 as thecapacitive coupling portion made of a dielectric material such asaluminum foil or copper foil. The line-to-line capacitance pattern 4formed on the back surface (i.e., the second main surface) of theantenna substrate 5 capacitively couples specific regions of the antennapattern 3 with each other at a plurality of points of the antennapattern 3 having an inductance component. As a result, a plurality of LCparallel resonant circuits S are formed, each being configured from aninductance component formed in a part of the antenna pattern 3 and acapacitance component formed between the line-to-line capacitancepattern 4 and a part of the antenna pattern 3, resulting in asubstantially series or parallel connection configuration. FIG. 1 showsan example of the antenna substrate 5 made of a transparent material, inwhich the antenna pattern 3 and the line-to-line capacitance pattern 4(i.e., broken line indications in FIG. 1) formed on the front and backof the antenna substrate 5 are depicted. The antenna substrate 5 may notbe made of the transparent material and may be made of a materialcapable of a capacitive coupling having at a desired capacitance betweenthe antenna pattern 3 and the line-to-line capacitance pattern 4.

FIG. 2 shows the front surface (first main surface) and the back surface(second surface) of the antenna substrate 5. FIG. 2A shows the antennapattern 3 formed on the front surface (first main surface) of theantenna substrate 5, while FIG. 2B shows the line-to-line capacitancepattern 4 as the capacitive coupling portion formed on the back surface(second main surface) of the antenna substrate 5.

As shown in FIG. 2A, the antenna pattern 3 in the first embodimentcomprises two land patterns 6 (i.e., references 6 a and 6 b) in contactwith the RFIC package 2 for electrical connection. The antenna pattern 3has a first antenna element 3 a and a second antenna element 3 b to makeup a dipole field antenna.

As shown in FIG. 2A, the first antenna element 3 a has a substantiallylinear shape pattern and is led from the first land pattern 6 a toextend in a meandering manner. The extension of the first land pattern 6a is directed toward longitudinal one end of the antenna substrate 5,with the tip in the extending direction of the first land pattern 6 abeing disposed at the longitudinal end of the antenna substrate 5. Thefirst antenna element 3 a has a λ/4 length of the communicationfrequency. If the communication frequency is 920 MHz for example, thelength from the first land pattern 6 a in the first antenna element 3 aup to the end of the antenna substrate 5 is approx. 50 mm.

The second antenna element 3 b of the antenna pattern 3 is led from thesecond land pattern 6 b to extend toward the longitudinal other end ofthe antenna substrate 5 in a meandering manner, with the tip in theextending direction of the second antenna element 3 b having a widenedportion 7. This widened portion 7 is a portion attached to an articleand, if attached to an article whose exterior surface has an exposedmetal material, e.g. a can product, allows the article exterior surfaceto function as a part of the antenna.

As shown in FIG. 2B, the line-to-line capacitance pattern 4 as thecapacitive coupling portion formed on the back surface (second mainsurface) of the antenna substrate 5 has a plurality of line-to-linecapacitance electrodes 4 a and 4 b different in shape in theconfiguration of the first embodiment. The line-to-line capacitancepattern 4 has a first line-to-line capacitance electrode 4 a of awidened shape and a second line-to-line capacitance electrode 4 b of anarrowed shape. The widely-shaped first line-to-line capacitanceelectrode 4 a capacitively couples specific confronting regions 3 aawith each other in the meandering first antenna element 3 a, andsimilarity capacitively couples specific confronting regions 3 ba witheach other in the meandering second antenna element 3 b. The firstline-to-line capacitance electrode 4 a is disposed so as to capacitivelycouple at least adjacent turn portions in the first antenna element 3 aand the second antenna element 3 b.

On the other hand, the narrowly-shaped second line-to-line capacitanceelectrode 4 b is disposed so as to capacitively couple a specific regionin the first antenna element 3 a and a specific region in the secondantenna element 3 b. The narrowly-shaped second line-to-line capacitanceelectrode 4 b is disposed so as to capacitively couple the first landpattern 6 a with a specific region in the first antenna element 3 a andis disposed so as to capacitively couple the second land pattern 6 bwith a specific region (including the widened portion 7) in the secondantenna element 3 b.

The thus configured antenna pattern 3 on the front surface (first mainsurface) of the antenna substrate 5 and line-to-line capacitance pattern4 on the back surface (second main surface) of the antenna substrate 5have a shape preventing concentration of the electric field and have nosharp edges particularly at bent portions and edge portions of the outerperiphery, the entirety being formed from gentle curved surfaces.

The RFID tag 1 in the first exemplary embodiment can be applied to allitems dealt in “convenience stores”, for example, and the RFID tag 1 ofthe same configuration is used for all of the items. For this reason, alunch box heated by “microwave oven” as microwave heating apparatus willbe described as an exemplification of goods in an exemplary of the firstembodiment. Such a lunch box also uses the RFID tag 1 having the widenedportion 7 that allows a metal material on the article exterior surfaceto function as a part of the antenna. FIG. 3A is a perspective viewshowing the case where the RFID tag 1 is attached to a lunch box 8 as anexemplification of an article configured from an insulator material.FIG. 3B shows an example where the RFID tag 1 is attached to a metal can14 as an example of an article whose exterior surface is made of a metalmaterial.

FIG. 4 is an exploded perspective view showing a configuration of theRFIC package 2 mounted on the land patterns 6 (6 a and 6 b) of theantenna pattern 3. As shown in FIG. 4, the RFIC package 2 in the firstembodiment is configured from a multi-layered substrate comprised ofthree layers. Specifically, the multi-layered substrate of the RFICpackage 2 is made of a resin material such as polyimide and liquidcrystal polymer and is configured from three laminated insulating sheets12A, 12B, and 12C having a flexibility. The insulating sheets 12A, 12B,and 12C have a substantially square shape in plan view and, in the firstembodiment, have a substantially rectangular shape. The RFIC package 2shown in FIG. 4 shows the state where the RFIC package 2 shown in FIG. 1is turned over with three layers decomposed.

As shown in FIG. 4, the RFIC package 2 includes, on its three-layeredsubstrate (insulating sheets 12A, 12B, and 12C) at desired positions, anRFIC chip 9, a plurality of inductance elements 10A, 10B, 10C, and 10D,and external connection terminals 11 (11 a and 11 b).

The external connection terminals 11 (11 a and 11 b) are formed on thefirst insulating sheet 12A that is the lowermost layer (substrateconfronting the antenna pattern 3) and are formed at positionsconfronting the land patterns 6 (6 a and 6 b) of the antenna pattern 3.The four inductance elements 10A, 10B, 10C, and 10D are formedseparately two by two on the second insulating sheet 12B and the thirdinsulating sheet 12C, respectively. In other words, the first inductanceelement 10A and the second inductance element 10B are formed on thethird insulating sheet as the uppermost layer (undermost layer in FIG.4), while the third inductance element 10C and the fourth inductanceelement 10D are formed on the second insulating sheet 12B as theintermediate layer.

In the RFIC package 2 of the first embodiment, the external connectionterminals 11 (11 a and 11 b) and the four inductance elements 10A, 10B,10C, and 10D are configured from a conductor pattern made of aconductive material such as aluminum foil or copper foil.

As shown in FIG. 4, the RFIC chip 9 is mounted on the third insulatingsheet 12C as the uppermost layer at its center portion in thelongitudinal direction (X-direction in FIG. 4). The RFIC chip 9 has astructure in which various types of elements are incorporated in asemiconductor substrate made of a semiconductor such as silicon. Thefirst inductance element 10A formed spirally on the third insulatingsheet 12C on its one side (left in X-axis direction in FIG. 4) isconnected via a land 10Aa to an input/output terminal 9 a on one hand ofthe RFIC chip 9. The second inductance element 10B formed spirally onthe third insulating sheet 12C on the other side (right in X-axisdirection in FIG. 4) is connected via a land 10Ba to an input/outputterminal 9 b on the other of the RFIC chip 9.

The third inductance element 10C in spiral shape is formed on the secondinsulating sheet 12B as the intermediate layer on its one side (left inX-axis direction in FIG. 4), while the fourth inductance element 10D inspiral shape is formed on the second insulating sheet 12B on the otherside (right in X-axis direction in FIG. 4). An outer peripheral end ofthe spirally-shaped third inductance element 10C connects directly to anouter peripheral end of the spirally-shaped fourth inductance element10D. On the other hand, an inner peripheral end (land 10Ca) of the thirdinductance element 10C connects, via an interlayer connection conductorsuch as a through-hole conductor passing through the second insulatingsheet 12B, to an inner peripheral end (land 10Ab) of the spirally-shapedfirst inductance element 10A on the third insulating sheet 12C. Theinner peripheral end (land 10Ca) of the third inductance element 10Cconnects, via an interlayer connection conductor such as a through-holeconductor extending through the first insulating sheet 12A as thelowermost layer, to the first external connection terminal 11 a on thefirst instructing sheet 12A.

An inner peripheral end (land 10Da) of the fourth inductance element 10Dconnects, via an interlayer connection conductor such as a through-holeconductor extending through the second insulating sheet 12B, to an innerperipheral end (land 10Bb) of the spirally-shaped second inductanceelement 10B on the third insulating sheet 12C. The inner peripheral end(land 10Da) of the fourth inductance element 10D connects, via aninterlayer connection conductor such as a through-hole conductorextending through the first insulating sheet 12A, to the second externalconnection terminal 11 b on the first insulating sheet 12A.

The first external connection terminal 11 a on the first insulatingsheet 12A is disposed so as to be connected to the first land pattern 6a of the first antenna element 3 a formed on the antenna substrate 5.Moreover, the second external connection terminal 11 b on the firstinsulating sheet 12A is disposed so as to be connected to the secondland pattern 6 b of the ax antenna element 3 b formed on the antennasubstrate 5.

As further shown, a through-hole 13 is formed in the second insulatingsheet 12B as the intermediate layer, for receiving the RFIC chip 9mounted on the third insulating sheet 12C. The RFIC chip 9 is formedfrom a semiconductor material and is disposed between the firstinductance element 10A and the second inductance element 10B and betweenthe third inductance element 10C and the fourth inductance element 10D.This allows the RFIC chip 9 to function as a shield, suppressing themagnetic field coupling and the capacitive coupling between the firstinductance element 10A and the second inductance element 10B, whilesimultaneously suppressing the magnetic field coupling and thecapacitive coupling between the third inductance element 10C and thefourth inductance element 10D. As a result, the RFIC package 2 in thefirst embodiment restrains the pass band of the communication signalfrom narrowing, rendering the pass band wide.

FIG. 5 is a diagram schematically showing, by circuit symbols, theline-to-line capacitance pattern 4 that is the capacitive couplingportion capacitively coupled with the antenna pattern 3 to which theRFIC package 2 is connected in the RFID tag 1 of the first embodiment.As shown in FIG. 5, the antenna pattern 3 is configured such that themeandering first antenna element 3 a and second antenna element 3 bextend with a plurality of turn portions from the land pattern 6 mountedwith the RFIC package 2. More specifically, the meandering first antennaelement 3 a extends from the first land pattern 6 a finally toward anend on one hand in the longitudinal direction (+X direction) in theantenna substrate 5. The meandering second antenna element 3 b extendsfrom the second land pattern 6 b finally toward an end on the other inthe longitudinal direction (−X direction) in the antenna substrate 5.The tip region in the extension direction of the second antenna element3 b is a widened portion 7 with a wide width that works as a portionattached to goods. The widened portion 7 is a region attached to a metalportion of a can product, etc. for example, to thereby further enhancethe characteristics of the antenna.

As shown in FIG. 5, the line-to-line capacitance pattern 4 capacitivelycoupling specific regions with each other in the first antenna element 3a and the second antenna element 3 b comprises the first line-to-linecapacitance electrode 4 a having a large capacitance and the secondline-to-line capacitance electrode 4 b having a smaller capacitance thanthe first line-to-line capacitance electrode 4 a. The first line-to-linecapacitance electrode 4 a capacitively couples specific regions witheach other in the first antenna element 3 a, to obtain the LC parallelresonant circuits S in the form of a loop circuit as a minimum pathconfigured from the first line-to-line capacitance electrode 4 a and thefirst antenna element 3 a. Thus, the plurality of LC parallel resonantcircuits are formed in series or in parallel with the path of the firstantenna element 3 a. Similarly, the first line-to-line capacitanceelectrode 4 a capacitively couples specific regions with each other inthe second antenna element 3 b, to form the plurality of LC parallelresonant circuits S in series or in parallel with the path of the secondantenna element 3 b.

Since the RFID tag 1 of the first exemplary embodiment is intended for alunch box, etc. in the convenience store as target goods, the case isassumed where the RFID tag 1 is dielectrically heated by a so-called“microwave oven” that is an electromagnetic wave heating device forcooking. Electromagnetic waves (microwave use frequencies) used in the“microwave oven” are in a frequency band of 2.4 to 2.5 GHz that is theband of higher frequencies than the communication frequency, andtherefore a “band elimination filter” is disposed as a circuit forremarkably attenuating this frequency band level in the RFID tag 1 ofthe first embodiment. The “band elimination filter” is a filter circuitattenuating the band of higher frequencies than the communicationfrequency and attenuates a higher frequency band than 1.1 GHz forexample. In particular, it remarkably attenuates frequencies (2.4 to 2.5GHz) of electromagnetic waves for heating used in the “microwave oven”.

As shown in FIG. 5, in the RFID tag 1 of the first embodiment,multi-stage (a plurality of) LC parallel resonant circuits S are formedalong paths of the first antenna element 3 a and the second antennaelement 3 b, these LC parallel resonant circuits S making up the “bandelimination filter”. Each LC parallel resonant circuit S in theplurality of LC parallel resonant circuits S is set so as to resonatewith frequencies in the frequency band of 2.4 to 2.5 GHz. The linelength of each LC parallel resonant circuit S is set to be shorter than½ frequency of the frequency used as the predetermined communicationfrequency. As shown in FIG. 5, the LC parallel resonant circuits S arearranged so as to configure a series circuit and a parallel circuit,with each LC parallel resonant circuit S being magnetically coupled orelectric field coupled with the other, to thereby greatly theelectromagnetic wave level in a wide band of 2.4 to 2.5 GHz band. FIG. 6is a diagram showing, in the form of a pseudo-equivalent circuit, apartial configuration example of the plurality of LC parallel resonantcircuits S in the RFID tag 1 of the first embodiment. FIG. 7 is adiagram showing, in the form of an equivalent circuit, an overallconfiguration example of the plurality of LC parallel resonant circuitsS in the wireless communication device of the first embodiment.

FIG. 8 is a frequency characteristic diagram showing the result ofsimulation experiments performed for the RFID tag 1 of the firstembodiment. FIG. 9 is an exemplary Smith chart in the simulationexperiments on the RFID tag 1 of the first embodiment. In the frequencycharacteristic diagram shown in FIG. 8, the frequency of 0.86 GHzindicated by ▾m1 had a power feed level of −10.2 dB, while the frequencyof 0.92 GHz indicated by ▾m2 had a power feed level of −9.1 B. For thefrequency of 2.4 GHz indicated by ▾m3 that is the frequency ofelectromagnetic waves for heating used in the “microwave oven”, thepower feed level is −49.6 dB, while for the frequency of 2.5 GHzindicated by ▾m4, it is −49.4 dB, from which it can be understood thatthe feed level is attenuated to a great extent. It can also beunderstood that the band of higher frequencies than the communicationfrequency is attenuated without being limited to 2.4 to 2.5 GHz. Forexample, regarding the frequency of approx. 1.2 GHz or more, the feedlevel is attenuated to −30 dB or below.

As shown in the Smith chart of FIG. 9, at the frequency of 0.86 GHzindicated by ▾m1 and the frequency of 0.92 GHz indicated by ▾m2, it isin the receivable state for impedance characteristics. As to the RFIDtag 1 of the first embodiment, it is obtained from the simulationexperiments that at the frequency of 2.4 GHz indicated by ▾m3 and thefrequency of 2.5 GHz indicated by ▾m4, it is in the substantiallyshort-circuited state (a marker lies at a point 0Ω at the left end inthe Smith chart).

As described above, it can be understood in the RFID tag 1 of the firstexemplary embodiment that a high-frequency signal (radio signal) havingUHF-band communication frequencies (900 MHz band, e.g. 920 MHz) is in atransmittable/receivable frequency band whereas the heating frequencies(2.4 to 2.5 GHz) used in the “microwave oven” as the electromagneticwave heating apparatus is in a frequency band where the power feed levelis attenuated to a great extent (approx. −50 dB).

Although in the RFID tag 1 of the first embodiment, the feed level isattenuated to a great extent (approx. −50 dB) at the heating frequencies(2.4 to 2.5 GHz) used in the “microwave oven”, the feed level is notcompletely zero. Specifically, when the RFID tag 1 of the firstembodiment is dielectrically heated together with an article by the“microwave oven”, an extremely small current flows through the antennapattern 3 (3 a and 3 b).

FIG. 10 is a diagram obtained from simulation experiments of the RFIDtag 1 of the first embodiment on how current flows (FIG. 10A) whenreceiving a signal of a UHF-band communication frequency (920 MHz) andon how current flows (FIG. 10B) when receiving a signal of a heatingfrequency (2.4 GHz) used in the “microwave oven”. FIG. 10 shows, byblack and white achromatic colors, the colored result of the magnitudeof current flowing through the antenna pattern 3 (3 a and 3 b) and theline-to-line capacitance patterns 4 (4 a and 4 c) upon reception.Although for this reason the discrimination is not easy in FIG. 10, asis apparent from the result of experiments by the inventors, currentflowing when receiving the signal of the heating frequency (2.4 GHz) wasremarkably smaller than current flowing when receiving the signal of thecommunication frequency (920 MHz). Since in FIG. 10 the color of theantenna pattern 3 (3 a and 3 b) in FIG. 10A becomes deeper than that inFIG. 10B, it can be understood that current flowing when receiving thesignal of the communication frequency (920 MHz) is larger than currentflowing when receiving the signal of the heating frequency (2.4 GHz).

FIG. 11 is a diagram showing directions in which, when the antennapattern 3 and the line-to-line capacitance patterns 4 (firstline-to-line capacitance electrode 4 a) receive the signal of theheating frequency (2.4 GHz), current tries to flow through the patterns(3 and 4). In FIG. 11, a solid-line arrow P indicates the direction ofcurrent flowing through the antenna pattern 3 when receiving the signalof the heating frequency (2.4 GHz). A broken-line arrow Q indicates thedirection of current which, when current indicated by the solid-linearrow P flows through the antenna pattern 3, flows through the “bandelimination filter” as the plurality of LC parallel resonant circuits Scomposed of the antenna pattern 3 and the line-to-line capacitancepatterns 4.

As shown in FIG. 11, when the RFID tag 1 is dielectrically heated toreceive the signal of the heating frequency (2.4 GHz) to allow currentindicated by the solid-line arrow P to flow through the antenna pattern3, current indicated by the broken-line arrow Q tries to flow throughthe antenna pattern 3 in each LC parallel resonant circuit S in theplurality of LC parallel resonant circuits S. Specifically, in each LCparallel resonant circuit S, current tries to flow in the oppositedirection (broken-line arrow Q) to the direction P (solid-line arrow) ofcurrent flowing through the antenna pattern 3. This results in a statewhere current-flows trying to flow through the antenna pattern 3 and theLC parallel resonant circuit S, respectively, offset each other,whereupon a phenomenon can be suppressed that the antenna pattern 3generates heat to a high temperature by a large current released fromthe antenna pattern 3 receiving electric power of the electromagneticwave heating apparatus. In the configuration of the RFID tag 1, even ifthe antenna pattern 3 is partly disconnected as a result of partial heatgeneration of the antenna pattern 3 and subsequent partial sublimationof the antenna pattern 3, since the LC parallel resonant circuits S areformed on the entire antenna pattern, the phenomenon can be suppressedthat a large current is fed into the antenna pattern 3 by theelectromagnetic wave heating apparatus, even though the antenna pattern3 severed by the disconnection receives electric power of theelectromagnetic wave heating apparatus. Thus, due to the establishmentof the relationship shown in FIG. 11 between the LC parallel resonantcircuits S and the antenna pattern 3 in the configuration of the RFIDtag 1, the phenomenon continues to be suppressed that theelectromagnetic wave heating apparatus feeds into the antenna pattern 3a large current enough to disconnect (divide) the antenna pattern intopieces that is enough short to the degree that the antenna pattern 3cannot finally receive electric power of the electromagnetic waveheating apparatus. As a result, even though the RFID tag 1 of the firstembodiment receives the signal of the heating frequency (2.4 GHz),current flowing through the antenna pattern 3 is attenuated to a greatextent (e.g. approx. −50 dB). Furthermore, in the loop circuit of the LCparallel resonant circuits S having the line-to-line capacitanceelectrodes 4 a arranged on the turn portions of the antenna pattern 3,current not offset by current flowing through the antenna pattern 3flows through the line-to-line capacitance electrodes 4 a. Since thiscurrent causes a magnetic field, a part of electric power fed to the LCparallel resonant circuits S is lost as magnetic field energy. As aresult, the RFID tag 1 of the first embodiment can have a circuitconfiguration allowing a remarkable attenuation for the band of theheating frequency (2.4 GHz) by the “band elimination filter” composed ofthe plurality of LC parallel resonant circuits S. The RFID tag 1 of thefirst embodiment has a circuit configuration similarly allowing aremarkable attenuation for the heating frequency band (2.4 to 2.5 GHz)used in the “microwave oven” as the electromagnetic wave heatingapparatus.

FIG. 12 is a diagram showing gains for all directions related to theRFID tag 1 of the first embodiment. It is noted that the X-direction inFIG. 12 indicates the longitudinal direction of the RFIC package 2 inthe RFID tag 1. As shown in FIG. 12, the RFID tag 1 has a higher gain inY-direction and Z-direction and has a wide directivity in Y-directionand Z-direction. The RFIC package 2 has a slightly lower gain in itslongitudinal direction (X-direction) only as compared with the otherdirections but has a generally wide directivity.

Although in the RFID tag 1 of the first embodiment, all LC parallelresonant circuits S in the plurality of LC parallel resonant circuits Sconfigured from the antenna pattern 3 and the line-to-line capacitancepatterns 4 are set so as to resonate with frequencies of the frequencyband (2.4 to 2.5 GHz) used in the electromagnetic wave heatingapparatus, in the exemplary embodiments of the present disclosure, allof the LC parallel resonant circuits S need not necessarily resonatewith frequencies used in the electromagnetic wave heating apparatus.Configuration may be such that in the case where the RFID tag 1 isdielectrically heated by the electromagnetic wave heating apparatus,current flowing through the antenna pattern 3 can be attenuated to agreat extent.

As described above, the RFID tag 1 of the first exemplary embodiment isa wireless communication device for transmitting/receiving ahigh-frequency signal having a predetermined communication frequency. Inthis aspect, the wireless communication device includes the antennapattern 3 having an inductance component; the RFIC chip 9 electricallyconnected to the antenna pattern 3; and the line-to-line capacitancepattern 4 as a capacitive coupling portion that capacitively couplestogether specific confronting regions 3 aa each facing the other of theantenna pattern 3, at a plurality of points of the antenna pattern 3.Using such a simple configuration, even though the RFID tag 1 isirradiated with an electromagnetic wave having a frequency higher thanthe communication frequency, the LC parallel resonant circuits Sfunction as the band elimination filter so that the irradiatedelectromagnetic wave higher than the communication frequency can greatlybe attenuated.

In the RFID tag 1 of the first embodiment that is a wirelesscommunication device, the “band elimination filter” is provided that iscomposed of the plurality of LC parallel resonant circuits S eachincluding the antenna pattern 3 as a metal film body disposed on bothsides of the dielectric and the line-to-line capacitance pattern 4 asthe capacitive coupling portion. For this reason, the RFID tag of thefirst embodiment is configured such that remarkable attenuation can beachieved for frequencies in the frequency band (2.4 to 2.5 GHz) used inthe electromagnetic wave heating apparatus.

Due to the formation of the line-to-line capacitance pattern 4 on theantenna pattern 3, the resonant frequency of the RFID tag 1 is adjustedto the UHF-band communication frequency. The resonant frequency by theantenna pattern 3 without formation of the line-to-line capacitancepattern 4 is higher than the communication frequency, e.g. approx. 1.1GHz.

Advantageously, the RFID tag 1 of the first embodiment is configuredsuch that when dielectrically heated by the electromagnetic wave heatingapparatus, a current flows through the loop circuit as a minimum pathcomposed of the antenna pattern 3 and the line-to-line capacitancepattern 4, this loop circuit acting as a small-sized magnetic fieldantenna at the frequency of the electromagnetic wave heating apparatusso as to less receive the electric field energy radiated from theelectromagnetic wave heating apparatus. Thus, the loop circuit alone isconfigured to be hard to ignite by the electromagnetic wave heatingapparatus and be able to lose, as the magnetic field energy, thereceived electric field energy (electric power). In consequence, theRFID tag 1 of the first embodiment becomes configured to be able togreatly attenuate the power feed level at the time of dielectricheating. Although the antenna pattern 3 is gradually heated by a minutecurrent flowing through the antenna pattern 3 irrespective of theremarkable attenuation of the power feed level, the antenna pattern 3can easily be disconnected by deformation of the antenna substrate 5 bysetting the line width of the antenna pattern 3 to about 100 μm to 300μm. As a result, the antenna substrate 5 deforms by heating of theantenna pattern 3 to disconnect the antenna pattern 3, so that theantenna pattern 3 goes disconnected till the time when the antennapattern 3 becomes unable to receive more electromagnetic wave of thedielectric heating, whereby the entire tag cannot burn in spite of thedielectric overheating of the RFID tag.

The RFID tag 1 of the first embodiment is configured such thatconcentration of the electric field is suppressed by the curved surfaceshape of the antenna pattern 3 and the line-to-line capacitance pattern4 and further such that the widely shaped first line-to-line capacitanceelectrode 4 a capacitively couples at least the adjacent turn portionsin the first antenna element 3 a and the second antenna element 3 b.Consequently, when the RFID tag 1 is dielectrically heated by theelectromagnetic wave heating apparatus, the concentration of electricfield can be suppressed in the turn portions of the first antennaelement 3 a and the second antenna element 3 b in particular.

By using the above configuration, also when an article with the RFID tag1 of the first embodiment is dielectrically heated in theelectromagnetic wave heating apparatus (microwave oven), the occurrenceof discharge in the RFID tag 1 is greatly suppressed, thereby preventingthe risk of ignition in the article.

Second Embodiment

Hereinafter, description will be given of an RFID tag 21 that is awireless communication device of a second exemplary embodiment. Asregards the RFID tag 21 of the second embodiment, differences from theRFID tag 1 of the first embodiment will mainly be described. Indescription of the second embodiment, elements having similarconfigurations, operations, and functions to those of the firstembodiment are designated by the same reference numerals and, in somecases, may not again be described for avoiding duplicate description.

The RFID tag 21 of the second embodiment differs in configuration of anantenna pattern 23 from the RFID tag 1 of the first embodiment, but theother configurations are substantially the same as those of the RFID tag1 of the first embodiment. FIG. 13 is a plan view showing aconfiguration of the RFID tag 21 of the second embodiment. The RFID tag21 is configured to make wireless communication by a high-frequencysignal having a UHF-band communication frequency (carrier frequency) andis configured to be capable of wireless communication in a widefrequency band.

The RFID tag 21 of the second embodiment differs from the RFID tag 1 ofthe first embodiment in that the linear antenna pattern 23 has atspecific regions a reduced sectional shape (sectional shape cut in adirection orthogonal to the extending direction). The RFID package 2 andthe antenna substrate 5 in the second embodiment are substantially thesame as those of the RFID tag 1 of the first embodiment.

As described in the first embodiment, configuration is such that in thecase where the RFID tag 21 is dielectrically heated in the “microwaveoven” that is an electromagnetic wave heating apparatus, the RFID tag 21attenuates the power feed level of the heating frequencies (2.4 to 2.5GHz) used in the “microwave oven” to a great extent (approx. −50 dB).Regardless of such a configuration of the RFID tag 21 in which the powerfeed level of the heating frequencies (2.4 to 2.5 GHz) is greatlyattenuated, an extremely small current flows through the antenna pattern23 because the power feed level is not zero. As a result, the antennapattern 23 generates heat by its own resistance. Particularly, in thecase where the RFID tag as the wireless communication device isdielectrically heated by the “microwave oven” over a long period of time(several minutes), the antenna pattern itself comes to have a hightemperature, and hence the antenna substrate, etc. may possibly ignite.

In the second embodiment, configuration is such that in the case wherethe RFID tag 21 as the wireless communication device is dielectricallyheated by the “microwave oven” over a long period of time (severalminutes), the antenna pattern 23 sublimates and severs at its specificportion. The RFID tag 21 of the second embodiment has a reducedsectional area on the linear antenna pattern 23 at its specific site(disconnection forming portion C). In other words, the antenna pattern23 has at its disconnection forming portion C a smaller sectional areaother than the other portions, of a section cut at its specific site ina direction orthogonal to the extending direction thereof. Thedisconnection forming portion C having a reduced sectional area can beformed by slimming (narrowing) or thinning the line of the antennapattern 23.

The specific configuration of the disconnection forming portion C can befor example a configuration where the wiring width at a specific site onthe antenna pattern 23 is formed to be partly slimmer to about 100 μm to50 μm, for example, as compared with the other portions, or aconfiguration where the thickness is thinned to 9 μm to 6 μm. Thus, afragile point is formed that easily break when the antenna substrate 5deforms. In this manner, the disconnection forming portion C having asmaller sectional area than the other portions on the antenna pattern 23is preferably a site between the line-to-line capacitance patterns thatare capacitive coupling portions in the LC parallel resonant circuits Sconfigured as the “band elimination filter”. According to the exemplaryaspect, each LC parallel resonant circuit S in the plurality of LCparallel resonant circuits S is set so as to resonate with frequenciesin the frequency band of 2.4 to 2.5 GHz. The line length of each LCparallel resonant circuit S is set to be shorter than ½ frequency of thefrequency used as the predetermined communication frequency and furtherto be ¼ wavelength (λ/4) or less of the frequency band of the heatingelectromagnetic wave (2.4 to 2.5 GHz). FIG. 13 shows an example in whichthe disconnection forming portion C is formed on the line of the antennapattern 3 between the line-to-line capacitance patterns 4 making up theLC parallel resonant circuits S.

Accordingly, in the case where the RFID tag 21 is dielectrically heatedfor a long period of time and consequently the antenna pattern 23sublimates and severs at the disconnection forming portion C, the linelength of the disconnected portions of the antenna pattern 23 becomes ¼wavelength (λ/4) or less of the frequency band of the heatingelectromagnetic wave (2.4 to 2.5 GHz), making it hard to receive theelectromagnetic wave as the heating electromagnetic wave (2.4 to 2.5GHz), whereby the LC parallel resonant circuit S is prevented fromfurther rising in temperature by the frequency (2.4 to 2.5 GHz) of theheating electromagnetic wave used in the “microwave oven”.

In the RFID tag 21 of the second embodiment, the antenna substrate 5 isdisposed between the antenna pattern 23 and the line-to-line capacitancepattern 24 so as to reliably secure the dielectric capacitance betweenthe antenna pattern 23 and the line-to-line capacitance pattern 24 evenin the case where the antenna pattern 23 rises in temperature to warmthe antenna substrate 5, the antenna substrate 5 being made of aheat-resistant adhesive label, e.g. a material such as a polyester-basedresin or a polyimide-based resin having a 200° C. or more ofheat-resistance temperature and a 5 minutes or more of durability. Afilm body formed from a heat-resistant material may intervene betweenthe antenna substrate 5 and the antenna pattern 23 and/or between theantenna substrate 5 and the line-to-line capacitance pattern 24, so asto further enhance the heat resistance.

The thus configured RFID tag 21 of the second embodiment prevents therisk of ignition therein even in the case where an article with the RFIDtag 21 is dielectrically heated in the electromagnetic wave heatingapparatus (microwave oven), thereby providing a wireless communicationdevice having a high safety and a high reliability.

Third Embodiment

Hereinafter, description will be given of an RFID tag 31 that is awireless communication device of a third exemplary embodiment. Asregards the RFID tag 31 of the third embodiment, differences from theRFID tag 1 of the first embodiment will mainly be described. Indescription of the third embodiment, elements having similarconfigurations, operations, and functions to those of the firstembodiment are designated by the same reference numerals and, in somecases, may not again be described for avoiding duplicate description.

The RFID tag 31 of the third embodiment differs greatly in shape of themeandering antenna pattern 33 from the RFID tag 1 of the firstembodiment. FIG. 14 is a plan view showing a configuration of the RFIDtag 31 of the third embodiment. The RFID tag 31 is configured forwireless communication using a high-frequency signal having a UHF-bandcommunication frequency (carrier frequency) and is configured to becapable of wireless communication in a wide frequency band.

The RFID tag 31 of the third embodiment has a more elongated shape inplan view than the RFID tag 1 of the first embodiment and is mounted atits center with the RFIC package 2. More specifically, an antennasubstrate 35 of the RFID tag 31 has an elongated shape, with an antennapattern 33 (first antenna element 33 a and second antenna element 33 b)being disposed on both sides of the RFIC package 2 mounted on theantenna substrate 35 at its center. The first antenna element 33 a isformed on the antenna substrate 35 in a region (right-hand region inFIG. 14) on one hand in the longitudinal direction and extends towardone end in the longitudinal direction in a meandering manner. On theother hand, the second antenna element 33 b is formed on the antennasubstrate 35 in a region (left-hand region in FIG. 14) on the other inthe longitudinal direction and extends toward the other end in thelongitudinal direction in a meandering manner.

In the RFID tag 31 of the third embodiment, a line-to-line capacitancepattern 34 as a capacitive coupling portion is disposed so as tocapacitively couple adjacent turn portions together in the meanderingfirst antenna element 33 a and second antenna element 33 b. In thismanner, the RFID tag 31 of the third embodiment comprises multi-stage (aplurality of) LC parallel resonant circuits S formed along respectivepaths of the first antenna element 33 a and second antenna element 33 bhaving an inductance component, these LC parallel resonant circuits Smaking up the “band elimination filter”. Each LC parallel resonantcircuit S of the plurality of LC parallel resonant circuits S in thethird embodiment is also set so as to resonate with frequencies in thefrequency band of 2.4 to 2.5 GHz used in the “microwave oven”. The linelength of each LC parallel resonant circuit S is set to be shorter than½ frequency of the frequency used as the predetermined communicationfrequency.

The RFID tag 31 of the third embodiment is formed such that in a loopcircuit as a minimum path configured from the antenna pattern 33 and theline-to-line capacitance patterns 34, the line length between theline-to-line capacitance patterns 34 disposed at confronting turnportions is shorter than ½ frequency of the frequency used as thepredetermined communication frequency and further is ¼ wavelength orless of the frequencies (λ) of the frequency band (2.4 to 2.5 GHz) usedin the “microwave oven”. That is, the line length between the turnportions on the paths of the first antenna element 33 a and the secondantenna element 33 b is set shorter to be ¼ wavelength (λ/4: approx. 30to 34 mm) or less of the wavelength (λ) of the frequency band (2.4 to2.5 GHz). Thus, the RFID tag 31 of the third embodiment can have asimple configuration like a small tape with narrow width, enabling alow-price, easy-to-handle wireless communication device to beconstructed.

FIG. 15 shows a variant of the third embodiment and is a plan viewshowing a configuration of an RFID tag 41 in which the RFIC chip 9 ismounted on an antenna pattern 43. The RFID tag 41 is configured forwireless communication using a high-frequency signal having a UHF-bandcommunication frequency (carrier frequency) and is configured to becapable of wireless communication in a wide frequency band. The RFID tag41 shown in FIG. 15 has a similar configuration to that of the RFID tag31 shown in FIG. 14 except that the RFIC chip 9 is mounted on theantenna pattern 43 formed on a loop portion 40. More specifically, anantenna substrate 45 of the RFID tag 41 has an elongated shape, with theantenna pattern 43 (first antenna element 43 a and second antennaelement 43 b) being disposed on both sides of the loop portion 40 formedon the antenna substrate 45 at its center. According to the exemplaryaspect, the RFID tag 41 also comprises multi-stage (i.e., a pluralityof) LC parallel resonant circuits S formed along respective paths of thefirst antenna element 43 a and second antenna element 43 b having aninductance component. Thus, these LC parallel resonant circuits S formthe “band elimination filter”.

Each LC parallel resonant circuit S of the plurality of LC parallelresonant circuits S in the RFID tag 41 shown in FIG. 15 is also set soas to resonate with frequencies in the frequency band of 2.4 to 2.5 GHzused in the “microwave oven”, with the line length of each LC parallelresonant circuit S is set to be shorter than ½ frequency of thefrequency used as the predetermined communication frequency.

In the RFID tag 41 shown in FIG. 15, the line length between theline-to-line capacitance patterns 44 disposed at the turn portions onthe paths of the meandering first antenna element 43 a and secondantenna element 43 b is set to ¼ wavelength (λ/4: approx. 30 to 34 mm)or less, with the RFID tag 41 having a tape-like shape with narrowwidth, providing an easy-to-handle wireless communication device that isnot an eyesore to the purchaser in the merchandise display.

As described above, the RFID tags 31 and 41 in the third embodimentprovides an easy-to-handle wireless communication device that does notbecome an obstacle to commodity display, having a high safety andreliability because of preventing the risk of ignition in the RFID tag31 and 41 even in the case where goods with the RFID tags 31 and 41 aredielectrically heated in the electromagnetic wave heating apparatus(microwave oven).

The RFID tags 31 and 41 described in the third embodiment may have aconfiguration where the disconnection forming portion C described in thesecond embodiment is formed on the antenna pattern 33 and 43. The RFIDtags 31 and 41 of the third embodiment have corner portions of acurved-surface shape for suppressing the concentration of electric fieldon the antenna pattern 3 and the line-to-line capacitance pattern 4.

Fourth Embodiment

Hereinafter, description will be given of an RFID tag 51 that is awireless communication device of a fourth exemplary embodiment. Asregards the RFID tag 51 of the fourth embodiment, differences from theRFID tag 1 of the first embodiment will mainly be described. Indescription of the fourth embodiment, elements having similarconfigurations, operations, and functions to those of the firstembodiment described above are designated by the same reference numeralsand, in some cases, may not again be described for avoiding duplicatedescription.

FIG. 16A is a plan view showing a configuration of the RFID tag 51 ofthe fourth embodiment. The RFID tag 51 is configured for wirelesscommunication using a high-frequency signal having an HF-bandcommunication frequency (carrier frequency) and is capable of wirelesscommunication in a wide frequency band. FIG. 16B is a diagram showing,in the form of an equivalent circuit, the configuration of an antennapattern (coil pattern) 53 in the RFID tag 51 of the fourth embodiment.

As shown in FIG. 16A, the RFID tag 51 comprises the antenna pattern 53having a matching circuit of the loop portion 50 provided with the RFICchip 9 and a capacitor element 52. In the matching circuit of the loopportion 50, the capacitor element 52 is connected at a position facingthe RFIC chip 9. An antenna element 53 a of the antenna pattern 53 inthe RFID tag 51 extends from the loop portion 50 and is formed into aspiral. The antenna element 53 a shown in FIG. 16A is led in a clockwiseinner winding manner from the loop portion 50. A tip as a leading end ofthe antenna element 53 a is directly connected via a bridge pattern 56to the matching circuit of the loop portion 50. An insulating pattern 57made of a heat-resistant electrically-insulating material is disposedbetween the bridge pattern 56 and the antenna pattern 53 so as to securethe insulation between the bridge pattern 56 and the antenna pattern 53.

In the spiral antenna element 53 a led from the matching circuit of theloop portion 50, the line-to-line capacitance pattern 54 as a pluralityof capacitive coupling portions capacitively coupling adjacent pathstogether is disposed at predetermined intervals along the path of thespiral antenna element 53 a. The insulating pattern 57 made of aheat-resistant electrically-insulating material is disposed between theline-to-line capacitance pattern 54 and the antenna element 53 a so asto secure the insulation between the line-to-line capacitance pattern 54and the antenna element 53 a.

As described above, the RFID tag 51 of the fourth embodiment comprisesmulti-stage (i.e., a plurality of) LC parallel resonant circuits Sformed along the path of the antenna element 53 a having an inductancecomponent, these LC parallel resonant circuits S making up the “bandelimination filter”. Each LC parallel resonant circuit S of theplurality of LC parallel resonant circuits S in the RFID tag 51 is alsoset so as to resonate with frequencies in the frequency band of 2.4 to2.5 GHz used in the “microwave oven”, with the line length of each LCparallel resonant circuit S being set to be shorter than ½ frequency ofthe frequency used as the predetermined communication frequency.

The RFID tag 51 of the fourth embodiment is configured such that theantenna pattern 53 and the line-to-line capacitance pattern 54 as thecapacitive coupling portion are laminated on the front surface (firstmain surface) of the antenna substrate 55 via the insulating pattern 57that is a dielectric. On the front surface (first main surface) of theantenna substrate 55, the bridge pattern 56 is formed via the insulatingpattern 57 on the antenna pattern 53, to make up the antenna of the RFIDtag 51. Thus, the plurality of patterns (53, 57, 56, and 54) are formedon the same surface of the antenna substrate 55, providing aconfiguration easy to manufacture the RFID tag 51. In the RFID tag 51 ofthe fourth embodiment, the antenna substrate 55 may not be made of adielectric, and it may be made of a paper material for example.

As described referring to FIG. 11 in the first embodiment, the RFID tag51 of the fourth embodiment also has a circuit configuration in whichthe “band elimination filter” composed of the plurality of LC parallelresonant circuits S can achieve a remarkable attenuation for frequenciesin the band of the heating frequency (2.4 to 2.5 GHz). Accordingly, theRFID tag 51 as the wireless communication device of the fourthembodiment is capable of wireless communication using a high-frequencysignal having a HF-band communication frequency (carrier frequency) and,even when an article with the RFID tag 51 is dielectrically heated inthe electromagnetic wave heating apparatus (microwave oven), cansuppress the occurrence of discharge in the RFID tag 51 to a greatextent, thereby enabling the risk of ignition in the article to securelybe prevented.

Fifth Embodiment

Hereinafter, description will be given of an RFID tag 61 that is awireless communication device of a fifth exemplary embodiment. Asregards the RFID tag 61 of the fifth embodiment, differences from theRFID tag 1 of the first embodiment will mainly be described. Indescription of the fifth embodiment, elements having similarconfigurations, operations, and functions to those of the firstembodiment are designated by the same reference numerals and, in somecases, may not again be described for avoiding duplicate description.

FIG. 17A is a plan view showing a configuration of the RFID tag 61 ofthe fifth embodiment. The RFID tag 61 is configured for wirelesscommunication using a high-frequency signal having a HF-bandcommunication frequency (carrier frequency) and is capable of wirelesscommunication in a wide frequency band. FIG. 17B is a diagram showing,in the form of an equivalent circuit, the configuration of two coilpatterns (63 and 73) including an antenna pattern in the RFID tag 61 ofthe fifth embodiment.

As shown in FIG. 17A, the RFID tag 61 of the fifth embodiment comprisesa resonant booster circuit having the two coil patterns (63 and 73). Thecoil pattern (primary coil pattern) 73 on one hand of the RFID tag 61has a matching circuit of a loop portion 70 provided with the RFIC chip9 and a capacitor element 72. In the matching circuit of the loopportion 70, the RFIC chip 9 is connected at a position facing thecapacitor element 72. The coil pattern (primary coil pattern) 72 is ledspirally from the loop portion 70, with a tip as a leading end thereofbeing directly connected via a bridge pattern 74 to the matching circuitof the loop portion 70. The coil pattern (primary coil pattern) 73 isled in a clockwise inner winding manner from the loop portion 70.

The bridge pattern 74 may be formed on the back surface (second mainsurface) of the antenna substrate 65 so that the tip as the leading endof the coil pattern (primary coil pattern) 73 is connected to the loopportion 70 via an interlayer connection conductor extending through theantenna substrate 65. Otherwise, in the case where the bridge pattern 74is formed on the front surface (first main surface), an insulatingpattern made of a heat-resistant electrically-insulating material may bedisposed between the bridge pattern 74 and the primary coil pattern 73to secure the insulation between the bridge pattern 74 and the primarycoil pattern 73.

The other coil pattern (secondary coil pattern) 63 in the RFID tag 61 ofthe fifth embodiment is formed so as to surround the coil pattern(primary coil pattern) 73 to configure an antenna element 63 a formed ina clockwise inner winding manner. In the spiral antenna element 63 a ofthe antenna pattern 63, line-to-line capacitance patterns 64 as aplurality of capacitive coupling portions capacitively coupling theadjacent paths together are disposed at predetermined intervals alongthe path of the antenna element 63 a.

The antenna pattern 63 in the RFID tag 61 of the fifth embodiment isformed on the front surface (first main surface) of the antennasubstrate 65. On the other hand, the line-to-line capacitance patterns64 as the capacitive coupling portions are formed on the back surface(second main surface) of the antenna substrate 65 made of a dielectric,to capacitively couple specific regions on the antenna element 63 a ofthe antenna pattern 63. A capacitor element 62 is disposed on theantenna element 63 a of the antenna pattern 63. An outer end and aninner end of the spiral antenna element 63 a are electrically connecteddirectly to each other, via an interlayer connection conductor 66extending through the antenna substrate 65, by a conductive path pattern67 formed on the back surface (second main surface) of the antennasubstrate 65. It is possible to simultaneously form the line-to-linecapacitance patterns 64 and the conductive path pattern 67 formed on theback surface (second main surface) of the antenna substrate 65.

As described above, in the RFID tag 67 of the fifth embodiment, themulti-stage (the plurality of) LC parallel resonant circuits S areformed along the path of the antenna element 63 a of the antenna pattern63 having an inductance component, these LC parallel resonant circuits Smaking up the “band elimination filter”. Each LC parallel resonantcircuit S of the plurality of LC parallel resonant circuits S in thethird embodiment is also set so as to resonate with frequencies in thefrequency band of 2.4 to 2.5 GHz used in the “microwave oven”. The linelength of each LC parallel resonant circuit S is set to be shorter than½ frequency of the frequency used as the predetermined communicationfrequency.

The thus configured RFID tag 61 of the fifth embodiment has a circuitconfiguration capable of remarkable attenuation for frequencies in theband of heating frequency (2.4 to 2.5 GHz) by the “band eliminationfilter” composed of the plurality of LC parallel resonant circuits S.Accordingly, the RFID tag 61 of the fifth embodiment is configured to becapable of wireless communication using a high-frequency signal having aHF-band communication frequency (carrier frequency) and is configured tobe able to greatly suppress the occurrence of discharge in the RFID tag61 even when an article with the RFID tag 61 is dielectrically heated inthe electromagnetic wave heating apparatus (microwave oven), therebymaking it possible to securely prevent the risk of ignition in thearticle.

Thus, as set forth using specific configurations in the embodiments,according to these embodiments, there can be provided a wirelesscommunication device having a high safety and reliability, suppressingthe occurrence of discharge in the wireless communication device evenwhen an article with the wireless communication device is heated in theelectromagnetic wave heating apparatus with the wireless communicationdevice being erroneously attached, thereby making it possible to preventthe risk of ignition of the wireless communication device and furtherthe risk of ignition in the article with the wireless communicationdevice. Therefore, the exemplary embodiments can construct a systemautomating accounting for items purchased and bagging thereof in shopssuch as convenience stores handling a wide variety of goods such asfoods and daily commodities and provides a wireless communication devicecapable of greatly advancing toward the practical use of “unmannedconvenience stores”.

Sixth Embodiment

Hereinafter, referring to FIG. 18, description will be given of an RFIDtag that is a wireless communication device of a sixth exemplaryembodiment. FIG. 18 is a plan view showing a configuration of a RFID tag81 of the sixth embodiment.

As regards the RFID tag 81 of the sixth embodiment, differences from theRFID tag 1 of the first embodiment will mainly be described. Indescription of the sixth embodiment, elements having similarconfigurations, operations, and functions to those of the firstembodiment are designated by the same reference numerals and, in somecases, may not again be described for avoiding duplicate description.The other configurations of the RFID tag 81 of the sixth embodiment thanthe following configurations are substantially the same as those of theRFID tag 1 of the first embodiment.

In the RFID tag 1 of the first embodiment, the antenna pattern 3 isformed on the front surface of the antenna substrate 5 while theline-to-line capacitance pattern 4 as the capacitive coupling portion isformed on the back surface. On the contrary, in the RFID tag 81 of thesixth embodiment, both an antenna pattern 83 and a line-to-linecapacitance pattern 85 are formed on the front surface of the antennasubstrate 5.

The antenna pattern 83 as a field-emission type antenna pattern isformed on the front surface of the antenna substrate 5. The antennapattern 83 includes a first antenna element 83 a having a meanderingantenna pattern that meanders with a plurality of turn portions 83 ac,and a second antenna element 83 b connected to a widened portion 7. Theturn portions 83 ac of the antenna pattern 83 are points at which theextending direction of the antenna pattern 83 is reversed. The antennaelement 83 a has the plurality of turn portions 83 ac. The first antennaelement 83 has rectilinear portions 83 aa parallel to the widthdirection (i.e., Y-direction) of the antenna substrate 5. Theline-to-line capacitance pattern 85 is formed between the adjacentrectilinear portions 83 aa of the first antenna element 83 a and betweenthe adjacent turn portions 83 ac. The interval between the antennaelement 83 a and the line-to-line capacitance pattern 85 is 150 μm forexample.

The line-to-line capacitance pattern 85 is formed from a conductivematerial such as aluminum foil and copper foil, similar to the antennapattern 83. When formed from aluminum foil, the thickness of theline-to-line capacitance pattern 85 is 6 μm for example. Theline-to-line capacitance pattern 85 is formed into a loop shape.

The line-to-line capacitance pattern 85 includes line-to-linecapacitance patterns 85 a and 85 b each having a different length in thewidth direction (Y-direction) of the antenna substrate 5. Theline-to-line capacitance patterns 85 a and 85 b have the longitudinaldirection and the lateral direction, and the longitudinal length of theline-to-line capacitance patterns 85 a and 85 b is formed shorter to be¼ wavelength or less of the frequency used in the electromagnetic waveheating. In the amplitude direction (Y-direction) of meandering of theantenna pattern 83, a length Wa of the first antenna element 83 a islonger than a length Wc1 of the line-to-line capacitance pattern 85 aand a length Wc2 of the line-to-line capacitance pattern 85 b. Theline-to-line capacitance pattern 85 is configured from an elongatedclosed loop pattern. Hence, in the case of acting as a magnetic fieldantenna, Q characteristics of the antenna coil become worse, with afunction to convert the magnetic field energy into heat due to themagnetic loss. This heat causes the antenna substrate 5 to deform bye.g. melting or carbonizing, to disconnect the line-to-line capacitancepattern 85 and disconnect part of the antenna pattern 83.

The antenna pattern 83 of the sixth embodiment comprises the two landpatterns 6 (6 a and 6 b) in contact with and for electrical connectionto the RFIC package 2. This allows the RFIC chip 9 and the antennapattern 83 included in the RFIC package 2 to electrically be connectedto each other. The antenna pattern 83 includes the first antenna element83 a and the second antenna element 83 b to configure a dipole electricfield antenna.

The first antenna element 83 a has a substantially linear shape patternand is led from the first land pattern 6 a to extend in the meanderingmanner. The extending direction of the first antenna element 83 a isdirected toward a longitudinal end of the antenna substrate 5. The tipin the extending direction of the first antenna element 83 a is locatedat the longitudinal end of the antenna substrate 5.

The second antenna element 83 b of the antenna pattern 83 is led fromthe second land pattern 6 b and extends rectilinearly toward thelongitudinal other end of the antenna substrate 5, with the tip in theextending direction of the second antenna element 83 b having thewidened portion 7. This widened portion 7 is a portion attached to anarticle and, when attached to an article on which exterior surface ametal material is exposed, e.g. a can product, allows the articleexternal surface to function as a part of the antenna.

For example, the first antenna element 83 a has the rectilinear portions83 aa parallel to the width direction (Y-direction) of the antennasubstrate 5 and extending in the amplitude direction of the meander. Therectilinear portion 83 aa has confronting portions 83 c that face eachother without intervention of the line-to-line capacitance patterns 85 aand 85 c, between the line-to-line capacitance patterns 85 a and 85 c inthe width direction (Y-direction) of the antenna substrate 5 and betweenthe adjacent rectilinear portions 83 aa in the longitudinal direction(X-direction) of the antenna substrate 5. By alternately arranging theline-to-line capacitance pattern 85 a and the line-to-line capacitancepattern 85 b between the rectilinear portions 83 aa depending onextension of the antenna pattern 83 in the longitudinal direction of theantenna substrate 5, the positions of the confronting portions 83 cshift in the width direction of the antenna substrate 5.

A looped shield pattern 87 is formed around the land pattern 6. Theshield pattern 87 is made of a conductive material such as aluminum foilor copper foil, similar to the antenna pattern 3. The shield pattern 87includes a completely closed loop-shaped first shield pattern 84 a and apartly interrupted second shield pattern 87 b.

The first shield pattern 87 a is a completely closed loop-shaped patternhaving a long side shorter than that of the line-to-line capacitancepatterns 85 a and 85 b. This subquadrate pattern is formed with a longside enough not ignite regardless of reception of an electromagneticwave in the band of higher frequencies than the communication frequency.A current flows through this first shield pattern 87 a in the directionof cancelling the magnetic field generated by current flowing betweenthe first antenna element 83 a and the land patterns 6 a and 6 b. Sincethis first shield pattern 87 a is closer to a square than theline-to-line capacitance patterns 85 a and 85 b, Q characteristics ofthe inductance element configured by this pattern are higher than Qcharacteristics of the inductance element formed by the line-to-linecapacitance patterns 85 a and 85 b, making it easy to suppress heatgeneration and ignition arising from the magnetic loss. As a result, dueto the arrangement of the first shield patterns 86 a at the centralportion of the antenna substrate 5 in the longitudinal direction, thereis no eddy-current-based heat generation leading to disconnection,irrespective of irradiation of electromagnetic wave in the band ofhigher frequencies than the communication frequency.

The second shield pattern 87 b is partly interrupted. A current flowsthrough this pattern as well in the direction of cancelling the magneticfield generated by current flowing between the first antenna element 83a and the land patterns 66 and 6 b. Due to partial interruption in thispattern, irradiation of electromagnetic waves in the band of higherfrequencies than the communication frequency brings about a dischargeand a spark at the interrupted portion, with the result that the antennaelement of the discharge portion of the antenna substrate 5 locallysublimates. Since the antenna pattern lies in the vicinity of thesublimated point, a function is presented of disconnecting theneighboring antenna pattern simultaneously with the sublimation of thebase.

Moreover, according to this exemplary aspect, an extended portion 83 abextending from the first land pattern 6 a of the first antenna element83 a and the second antenna element 83 b extending from the second landpattern 6 b are arranged in the directions intersecting each other, e.g.orthogonal directions. This can reduce the occurrence of potentialdifference between the extended portion 83 ab of the first antennaelement and the second antenna element 83 b.

The thus configured antenna pattern 83, line-to-line capacitance pattern85, and shield pattern 87 on the front surface of the antenna substrate5 have a shape preventing the concentration of the electric field andhave no sharp edges particularly at bent portions and edge portions ofthe outer periphery, the entirety being formed from gentle curvedsurfaces.

Although in the first embodiment the mode has been exemplified where theRFIC package 2 is mounted on the antenna pattern 83, the RFIC chip 9 maydirectly be mounted on the antenna pattern 83. At this time, theinductor configured as the plurality of inductance elements 10A, 10B,10C, and 10D in the RFIC package 2 may be configured as a looped patternon the antenna substrate 5.

FIG. 19 is a plan view showing a part of the antenna pattern 83 of FIG.18. FIG. 19B is an equivalent circuit diagram of the antenna pattern 83shown in FIG. 19A. FIG. 19C is an explanatory view showing a currentflowing through FIG. 19A when receiving an electromagnetic wave in theband of higher frequencies than the communication frequency.

As shown in FIG. 19B, the line-to-line capacitance pattern 85 generatingcapacitance between specific regions of the first antenna element 83 aincludes the line-to-line capacitance pattern 85 a and the line-to-linecapacitance pattern 85 b having a circumferential length shorter thanthat of the line-to-line capacitance pattern 85 a. The line-to-linecapacitance patterns 85 a and 85 b are arranged between confrontingregions of the antenna pattern 83, spaced apart from each other alongthe direction of extension of the antenna pattern 83. The line-to-linecapacitance patterns 85 a and 85 b generate capacitance between specificconfronting regions of the first antenna element 83 a. Thus, the LCparallel resonant circuit S is configured from the line-to-linecapacitance patterns 85 a arranged between confronting portions facingeach other of the first antenna element 83 a. In other words, the LCparallel resonant circuit S is configured from part of the antennapattern 83 including the confronting regions sandwiching theline-to-line capacitance pattern 85 therebetween and the line-to-linecapacitance pattern 85. The plurality of LC parallel resonant circuits Sare formed in series with and in parallel with the path of the firstantenna element 83 a. These plural LC parallel resonant circuits Sresonate at a frequency in the band of higher frequencies than thecommunication frequency.

Inductance Lm shows an inductance component lying in a distributedmanner on the first antenna element 83 a. Inductance Ln shows aninductance component lying in a distributed manner on the line-to-linecapacitance pattern 85. The inductance Lm of the first antenna element83 and the inductance Ln of the line-to-line capacitance pattern 85confronting each other are magnetically coupled together. The firstantenna element 83 a and the line-to-line capacitance pattern 85 have anelectrostatic capacity Cs1 therebetween. Since the adjacent rectilinearportions 83 aa of the first antenna element 83 a and the line-to-linecapacitance pattern 85 have their respective electrostatic capacitiesCs1 therebetween, these electrostatic capacities Cs1 capacitively couplethe adjacent rectilinear portions 83 aa of the first antenna element 83a together. Let Cs2 be the electrostatic capacity between the adjacentrectilinear portions 83 aa. Due to the arrangement of the line-to-linecapacitance patterns 85 between the wiring pattern of the first antennaelement 83 a, the confronting portions 83 c of the first antenna element83 a having no line-to-line capacitance pattern 85 therebetween do notinclude portions cancelling the eddy current, thus maximizing theeddy-current-based potential difference without cancelling the magneticfield between the adjacent rectilinear portions 83 aa.

When the antenna pattern 83 is irradiated with an electromagnetic wavein the band of higher frequencies than the communication frequency, asshown in FIG. 19C, reverse currents flow through the first antennaelement 83 a with respect to the confronting portion 83 c as a border bythe electrostatic capacity Cs2. These currents increase the potentialdifference between the confronting portions 83 c.

Due to the electromagnetic field coupling between the first antennaelement 83 a and the line-to-line capacitance pattern 85, eddy currentsflow, inside the line-to-line capacitance pattern 85, in the reversedirection to the adjacent first antenna element 83 a. This eddy currentinduces the generation of a magnetic field. This generation of themagnetic field turns a part of electric power fed to the LC parallelresonant circuit into a magnetic field energy, allowing heat to begenerated by the magnetic loss of the line-to-line capacitance pattern85, resulting in a gradual energy loss. Since the band of higherfrequencies than the communication frequency can be attenuated in thismanner, the LC parallel resonant circuit functions as the bandelimination filter.

The RFID tag 81 of the sixth embodiment is directed to a lunch box, etc.in the convenience stores for example, as application commodities, andhence it is assumed that the RFID tag 81 is dielectrically heated by theso-called “microwave oven” that is an electromagnetic wave heatingapparatus for cooking. The use frequency of the microwave as anelectromagnetic wave used in the “microwave oven” is in the band offrequencies of 2.4 to 2.5 GHz that is the band of higher frequenciesthan the communication frequency. Accordingly, the RFID tag 81 of thesixth embodiment comprises the “band elimination filter” as a circuitfor attenuating this frequency band level to a great extent. The “bandelimination filter” is a filter circuit that attenuates the band ofhigher frequencies than the communication frequency. The RFID tag 81 ofthe sixth embodiment attenuates a frequency band higher than 1.1 GHz forexample. In particular, a remarkable attenuation is achieved for thefrequencies (2.4 to 2.5 GHz) of the heating electromagnetic wave used inthe “microwave oven”. The “band elimination filter” is configured byarranging the looped conductor patterns between the confronting regionsof the antenna pattern. Furthermore, by arranging, in the vicinity of anelectric field radiation antenna, closed loop-shaped conductor patternsacting as a magnetic field antenna at a frequency of the heatingelectromagnetic wave, the antenna radiation efficiency of the electricfield radiation antenna at a frequency of the heating electromagneticwave is attenuated to a great extent, rendering hard the reception ofenergy of the heating electromagnetic wave. In this case, thecircumferential length of the looped conductor pattern is smaller than ½wavelength of the UHF-band frequency used for communication. This allowsthe conductor pattern to behave as a magnetic field antenna at afrequency higher than the UHF-band frequencies so that the radiationefficiency in the band of higher frequencies than the UHF-bandfrequencies can be attenuated. The difference between thecircumferential length of the looped conductor pattern and ½ wavelengthof the frequency of the heating electromagnetic wave may be smaller thanthe difference between the circumferential length of the loopedconductor pattern and ½ wavelength of the UHF-band frequencies used incommunication. In consequence, the radiation efficiency in the vicinityof the frequency of the heating electromagnetic wave can be moreattenuated than that near the UHF-band frequencies.

The operation principle of the band elimination filter will be describedin more detail. As shown in FIGS. 18 and 19B, in the RFID tag 81 of thesixth embodiment, the line-to-line capacitance pattern 85 as the loopedconductor pattern is disposed between confronting regions of the antennapattern 83 so that a plurality of LC parallel resonant circuits S areformed along the path of the first antenna element 83 a, these LCparallel resonant circuits S making up the “band elimination filter”.Each LC parallel resonant circuit S of a plurality of LC parallelresonant circuits S is set to parallel-resonate with frequencies in thefrequency band of 2.4 to 2.5 GHz so as to act as the magnetic fieldantenna. The line length of each LC parallel resonant circuit S is setshorter than ½ wavelength (λ/2) of the frequency (2.4 to 2.5 GHz) of theheating electromagnetic wave used in the “microwave oven”. The LCparallel resonant circuits S are arranged to make up a series circuitand a parallel circuit, with the parallel resonant circuits S beingformed for magnetic coupling or electric field coupling with each otherso as to act as a magnetic field antenna in a wide band of 2.4 to 2.5GHz, thereby configuring a plurality of magnetic field antennas in thevicinity of the first antenna element 83 a acting as the electric fieldantenna. Since this magnetic field antenna and the first antenna element83 a acting as the electric field antenna are coupled together by theelectrostatic capacity, the first antenna element 83 a is allowed atrespective portions of the pattern to partially act as a magnetic fieldantenna. For this reason, the antenna radiation characteristics of thefirst antenna element 83 a as the electric field antenna pattern sharplydeteriorate. The reception energy of the first antenna element 83 a asthe electric field antenna pattern is consumed in the heat by themagnetic field antenna. This attenuates the electromagnetic wavereception level of the electric field antenna pattern and disperses theheat generation points. The circumferential length of the line-to-linecapacitance patterns 85 a and 85 b is set so as to be shorter than ½wavelength (λ/2) of the frequency (2.4 to 2.5 GHz) of the heatingelectromagnetic wave.

FIG. 28 is a frequency characteristic diagram showing the result ofsimulation experiments effected on the RFID tag 81 of the sixthembodiment. FIG. 29 is an exemplary Smith chart in the simulationexperiments on the RFID tag 81 of the sixth embodiment. In the frequencycharacteristic diagram of the antenna radiation efficiency shown in FIG.28, the power feed level was −10 dB at the frequency of 0.86 GHzindicated by ▾m1, while the power feed level was −9.6 dB at thefrequency of 0.92 GHz indicated by ▾m2. The power feed level is −53 dBat the frequency of 2.4 GHz designated by ▾m3, which is the frequency ofthe heating electromagnetic wave used in the “microwave oven”, while itis −54 dB at the frequency of 2.4 GHz designated by ▾m4, from which itcan be seen that the power feed level is attenuated to a great extent.It can also be understood that the band of higher frequencies than thecommunication frequency is attenuated without being limited to 2.4 to2.5 GHz. For example, the frequency of approx. 1.2 GHz or more isattenuated to −30 dB or more.

As shown in the Smith chart of FIG. 29, at the frequency of 0.86 GHzindicated by ▾m1 and at the frequency of 0.92 GHz indicated by ▾m2, itis in the receivable state for impedance characteristics. As to the RFIDtag 81 of the sixth embodiment, it is obtained from the simulationexperiments that at the frequency of 2.4 GHz indicated by ▾m3 and thefrequency of 2.5 GHz indicated by ▾m4, it is in the substantiallyshort-circuited state (a marker lies at a point 0Ω at the left end inthe Smith chart).

As described above, it can be understood in the RFID tag 8 of the sixthembodiment that a high-frequency signal (radio signal) having UHF-bandcommunication frequencies (900 MHz band, e.g. 920 MHz) is in atransmittable/receivable frequency band whereas the heating frequencies(2.4 to 2.5 GHz) used in the “microwave oven” as the electromagneticwave heating apparatus is in a frequency band where the power feed levelis attenuated to a great extent (approx. −50 dB). This shows that thepower of 1000 W of electromagnetic wave heating apparatus is attenuatedto 0.1 or below and shows that sharp overheating and ignition are hardto occur.

In this manner, in the RFID tag 81 of the sixth embodiment, the feedlevel is attenuated to a great extent (approx. −50 dB) at the heatingfrequencies (2.4 to 2.5 GHz) used in the “microwave oven”, but the feedlevel is not completely zero. Specifically, when the RFID tag 81 of thesixth embodiment is dielectrically heated together with an article bythe “microwave oven”, an extremely small current flows through theantenna pattern 83 (83 a and 83 b). This extremely small current istransmitted from the antenna pattern 83 to the line-to-line capacitancepattern 85 by the capacitive coupling and generates heat by the magneticloss of the line-to-line capacitance pattern 85 forming the magneticfield antenna, leading to a gradual energy loss. As a result, theantenna substrate 5 deforms by melting or carbonizing, to disconnect theline-to-line capacitance pattern 85 and/or a part of the antenna pattern83. Since this disconnection of the antenna pattern 83 occurs betweenthe closed loops of the line-to-line capacitance patterns 85, theantenna pattern 83 is divided to an electrical length of ¼ wavelength(λ/4) or less of the heating frequency (2.4 to 2.5 GHz). This patterndisconnection makes it more difficult that the antenna pattern 83receives the heating frequency (2.4 to 2.5 GHz).

FIG. 30A is a diagram obtained from simulation experiments of the RFIDtag 81 of the sixth embodiment on how current flows when receiving asignal of a UHF-band communication frequency (920 MHz). FIG. 30B is adiagram obtained from simulation experiments on how current flows whenreceiving a signal of a heating frequency (2.4 GHz) used in the“microwave oven”. FIGS. 30A and 30B show, by black and white achromaticcolors, the one-color-indicated result of the magnitude of currentflowing through the antenna pattern 83 (83 a and 83 b) and theline-to-line capacitance patterns 85 (85 a and 85 c) upon reception. Asshown in FIG. 30A, it can be seen that when irradiated with an UHF-bandelectric field, current concentrates at the antenna element 83 a of theantenna pattern 83 so that the antenna element 83 a functions as theantenna. As shown in FIG. 30B, it can be seen that when irradiated withan electric field of 2.4 GHz, the energy is dispersed among the antennaelement 83 a of the antenna pattern 83, the line-to-line capacitancepatterns 85 a and 85 b, and the shield pattern 87.

FIG. 31A is a diagram showing gains for all directions related to theRFID tag 81 of the sixth embodiment. X-direction in FIG. 31A representsthe longitudinal direction of the RFIC package 2 in the RFID tag 81. Asshown in FIGS. 31A and 31B, the RFID tag 81 has a higher gain inY-direction and Z-direction and has a wide directivity in Y-directionand Z-direction. The RFIC package 2 has a slightly lower gain in itslongitudinal direction (X-direction) only as compared with the otherdirections but has a generally wide directivity.

Although in the RFID tag 81 of the sixth embodiment, all LC parallelresonant circuits S in the plurality of LC parallel resonant circuits Sconfigured from the antenna pattern 83 and the line-to-line capacitancepatterns 85 are set so as to resonate with frequencies of the frequencyband (2.4 to 2.5 GHz) used in the electromagnetic wave heatingapparatus, in the exemplary embodiments of the present disclosure, allof the LC parallel resonant circuits S need not necessarily resonatewith frequencies used in the electromagnetic wave heating apparatus.Configuration may be such that in the case where the RFID tag 1 isdielectrically heated by the electromagnetic wave heating apparatus,current flowing through the antenna pattern 83 can be attenuated to agreat extent.

As described above, the RFID tag 81 as the wireless communication deviceof the sixth embodiment is a wireless communication device fortransmitting/receiving a high-frequency signal having a first frequencyof e.g. 900 MHz band for communication. The RFID tag 81 comprises thefirst antenna element 83 a of the antenna pattern 83 having rectilinearportions as confronting regions each facing the other; and the RFIC chip9 connected electrically to the antenna pattern 83. The RFID tag 81comprises the line-to-line capacitance pattern 85 a as a loopedconductor pattern disposed between the confronting regions of the firstantenna element 83 a. The circumferential length of the line-to-linecapacitance pattern 85 a is smaller than ½ wavelength of theelectromagnetic wave of the first frequency. The antenna pattern 83 andthe line-to-line capacitance pattern 85 make up the “band eliminationfilter” of the LC parallel resonant circuit S. For this reason, even ifthe RFID tag 81 is irradiated with an electromagnetic wave of a secondfrequency higher than the first frequency, the line-to-line capacitancepattern 85 a acting as the magnetic field antenna generates a magneticfield, so that the energy of the electromagnetic wave of the secondfrequency can be reduced. If even a single line-to-line capacitancepattern 85 a is disposed on the RFID tag 81, the energy irradiatedaround the line-to-line capacitance pattern 85 a can be reduced, so thatthe goods around the line-to-line capacitance pattern 85 a can beprevented from flaring up.

When the RFID tag 81 of the sixth embodiment is dielectrically heated bythe electromagnetic wave heating apparatus, inducted current flowsthrough the looped line-to-line capacitance pattern 85. Thus, thisline-to-line capacitance pattern 85 functions as a small-sized magneticfield antenna at the frequency of the electromagnetic wave heatingapparatus, providing a configuration where the electric field energyradiated from the electromagnetic wave heating apparatus is reflectedand is hard to receive. As a result, the RFID tag 81 is configured to behard to ignite by the electromagnetic wave heating apparatus and furtherto be able to reflect or lose the received electric field energy(electric power) in the form of magnetic field energy. Accordingly, theRFID tag 81 of the sixth embodiment is configured to be able toattenuate the power feed level to a large extent at the time ofdielectric heating.

By arranging a plurality of line-to-line capacitance patterns as thelooped conductor patterns, the RFID tag 81 can further reduce the energyirradiated around the antenna pattern 83. Since the adjacentline-to-line capacitance patterns 85 a and 85 b have their respectivedifferent circumferential lengths, the line-to-line capacitance patterns85 a and 85 b provide their respective different magnetic field antennafrequencies, generally configuring a wide band magnetic field antenna of2.4 GHz to 2.5 GHz band or above. The first resonant frequency by theline-to-line capacitance pattern 85 a and part of the antenna pattern 83including the confronting regions sandwiching the line-to-linecapacitance pattern 85 a therebetween is different from the secondresonant frequency by the line-to-line capacitance pattern 85 b andanother part of the antenna pattern 83 including confronting regionssandwiching therebetween the other line-to-line capacitance pattern 85 barranged adjacent to the line-to-line capacitance pattern 85 a. Thus, byattaching the RFID tag to a commodity, even though deviation of theresonant frequency occurs by the dielectric constant of the commodity,it is possible to configure a magnetic field antenna interfering withthe electric field antenna and to reduce the electromagnetic waveenergy.

Due to the formation of the line-to-line capacitance pattern 85 for theantenna pattern 83, the resonant frequency of the RFID tag 81 isfine-tuned. For example, as compared with the resonant frequency (880MHz) of the antenna pattern 83 in the case of absence of theline-to-line capacitance pattern 85, the antenna resonant frequencybecomes higher (approx. 980 MHz) by several 10 MHz because of theformation of the line-to-line capacitance pattern 85.

The RFID tag 81 of the sixth embodiment is configured such that theantenna pattern 83 and the line-to-line capacitance pattern 85 are of acurved surface shape to suppress the concentration of electric field,with the line-to-line capacitance pattern 85 a being arranged betweenadjacent turn portions 83 ac of at least the first antenna element 83 aand the second antenna element 83 b, so that when the RFID tag 81 isdielectrically heated by the electromagnetic wave heating apparatus, theconcentration of electric field in the turn portions 83 ac of the firstantenna element 83 a in particular is suppressed.

The above configuration greatly suppresses the occurrence of dischargein the RFID tag 81 of the sixth embodiment even in the case where anarticle with the RFID tag 81 is dielectrically heated in theelectromagnetic wave heating apparatus (microwave oven), therebypreventing the risk of ignition in the article.

When the potential difference between the confronting portions 83 cexceeds a certain magnitude, a discharge occurs between the confrontingportions 83 c. Accordingly, if irradiated with electromagnetic wavehaving large energy as from the microwave oven for example, a dischargeoccurs between the confronting portions 83 c, allowing the confrontingportions 83 c to be disconnected by heat of the discharge. The firstantenna element 83 c is designed to have a resistance of the levelinducing disconnection by the discharge. The antenna substrate 5 has athickness deformable by heat of the discharge. The thickness of theantenna substrate 5 is 38 μm for example. Since the shape of the antennapattern 3 on the antenna substrate 5 also deforms in accordance with thedeformation of the antenna substrate 5, resonance with theelectromagnetic wave irradiated is prevented.

In the case of using the PET film as the antenna substrate 5, theantenna substrate 5 in the confronting portions 83 c melts by energystrengthening its electric field between the confronting portions 83 c.The molten antenna substrate 5 immediately under the antenna pattern 3in the confronting portions 83 pulls the antenna pattern to cause itsdisconnection. Thus, previous to the occurrence of a discharge betweenthe confronting portions 83 c, the antenna pattern 3 disconnects at theconfronting portions 83 c.

It is noted that these disconnections occur simultaneously at aplurality of points of the confronting portions 83 c at the initialstage prior to the heating of the entire antenna substrate 5. Therefore,since the first antenna element 83 a disconnects simultaneously atplural points, current cannot flow through the first antenna element 83a, thereby preventing the temperature of the entire antenna substrate 5from rising to cause ignition.

The length from confronting portions 83 c as one end of the rectilinearportion 83 aa of the antenna element 83 a between the line-to-linecapacitance pattern 85 a and the line-to-line capacitance pattern 85 bup to the next confronting portions 83 c as the other end thereof is setto be ¼ wavelength (λ/4) of the frequency band of the frequencies (2.4to 2.5 GHz) of the heating electromagnetic wave. Accordingly, in thecase of disconnection at respective confronting portions 83 c, therespectively finely disconnected antenna elements 83 a are hard toabsorb radio waves of frequencies of the heating electromagnetic wave,whereby a discharge can be prevented from occurring at the antennapattern 83 after the disconnection.

The positions of the confronting portions 83 c shift alternately in thewidth direction (Y-direction) of the antenna substrate 5 in accordancewith the position of the antenna substrate 5 in the longitudinal(X-direction), the disconnected portions on the first antenna element 83a also appear alternately. This disperses heat generating points arisingfrom disconnection on the antenna substrate 5, to thereby prevent thedisconnected portions from linking with each other to cause ignition.

The electrostatic capacity Cs2 is formed only between the rectilinearportions 83 aa of the adjacent first antenna elements 83 a. In otherwords, the electrostatic capacity Cs2 is not formed between therectilinear portions 83 aa of the first antenna element 83 a, beyond oneor more rectilinear portions 83 aa in the longitudinal direction of theantenna substrate 5. Advantageously, t when the confronting portions 83c are disconnected, current flow between the rectilinear portions 83 aabeyond one or more rectilinear portions 83 aa can be prevented.

Due to the formation of the antenna pattern 83 and the line-to-linecapacitance pattern 85 on one surface of the antenna substrate 5, onlythe one surface can be subjected to an etching process for patternformation in manufacturing processes. The line-to-line capacitancepattern 85 may be formed on the back surface of the antenna substrate 5.Two or more line-to-line capacitance patterns 85 may be arranged in theconfronting direction between respective rectilinear portions 83 aa ofthe adjacent first antenna elements 83.

Seventh Embodiment

Hereinafter, referring to FIG. 20, description will be given of an RFIDtag 91 that is a wireless communication device of a seventh exemplaryembodiment. FIG. 20 is a plan view showing a configuration of the RFIDtag 91 of the seventh embodiment.

As regards the RFID tag 91 of the seventh embodiment, differences fromthe RFID tag 81 of the sixth embodiment will mainly be described. Indescription of the seventh embodiment, elements having similarconfigurations, operations, and functions to those of the sixthembodiment are designated by the same reference numerals and, in somecases, may not again be described for avoiding duplicate description.

Although the RFID tag 81 of the sixth embodiment has two line-to-linecapacitance patterns 85 a and 85 b along the extending direction of thefirst antenna element 83 a, between the rectilinear portions 83 aa ofthe first antenna element 83 a, it may comprise three or moreline-to-line capacitance patterns. The RFID tag 91 of the seventhembodiment comprises three line-to-line capacitance patterns as anexample. Although the lengths in the longitudinal direction(Y-direction) of the line-to-line capacitance patterns 85 a and 85 b ofthe sixth embodiment were the length of about half of the rectilinearportions 83 aa of the antenna pattern 83, the lengths in thelongitudinal direction of the line-to-line capacitance patterns 83 c and85 d of the seventh embodiment are even shorter. Although the RFID tag81 of the sixth embodiment has comprised the second shield pattern, allthe shield pattern of the RFID tag 91 of the seventh embodiment is afirst shield pattern 87 a. The other configurations are substantiallythe same as those of the RFID tag 1 of the first embodiment.

By dividing the line-to-line capacitance pattern 85 b into line-to-linecapacitance patterns 85 c and 85 d having shorter longitudinal lengthsfor arrangement, it is possible to increase the points of theconfronting portions 83 c and to increase the points where a dischargeoccurs. This enables the discharge points to be changed depending on thetype of the band of higher frequencies than the communication frequency.

Since the configuration of the seventh embodiment also generates eddycurrent and therefore a magnetic field at the line-to-line capacitancepatterns 85 a, 85 c, and 85 d when receiving a frequency higher than thecommunication frequency, a part of the fed electric power is lost as themagnetic field energy. Since the first antenna element 83 a can bedisconnected by increasing the potential difference between theconfronting portions 83 c to eventually cause a discharge, it can beprevented that the entire RFID tag 91 ignites.

Eighth Embodiment

Hereinafter, referring to FIG. 21, description will be given of an RFIDtag 101 that is a wireless communication device of an eighth exemplaryembodiment. FIG. 21 is a plan view showing a configuration of the RFIDtag 101 of the eighth embodiment.

As regards the RFID tag 101 of the eighth embodiment, differences fromthe RFID tag 91 of the seventh embodiment will mainly be described. Indescription of the eighth embodiment, elements having similarconfigurations, operations, and functions to those of the seventhembodiment are designated by the same reference numerals and, in somecases, may not again be described for avoiding duplicate description.

Although in the RFID tag 91 of the seventh embodiment, the first landpattern 6 a and the second land pattern 6 b have been juxtaposed in thewidth direction on the antenna substrate 5, in the RFID tag 101 of theeighth embodiment the first land pattern 6 a and the second land pattern6 b are arranged side by side in the longitudinal direction on theantenna substrate 5. The other configurations are substantially the sameas those of the RFID tag 91 of the seventh embodiment.

Since the configuration of the eighth embodiment also generates eddycurrent and therefore a magnetic field at the line-to-line capacitancepatterns 85 a, 85 c, and 85 d when receiving a frequency higher than thecommunication frequency, a part of the fed electric power is lost as themagnetic field energy. Since the first antenna element 83 a can bedisconnected by increasing the potential difference between theconfronting portions 83 c to eventually cause a discharge, it can beprevented that the entire RFID tag 101 ignites.

Ninth Embodiment

Hereinafter, referring to FIG. 22, description will be given of an RFIDtag 111 that is a wireless communication device of a ninth exemplaryembodiment. FIG. 22 is a plan view showing a configuration of the RFIDtag 111 of the ninth embodiment.

As regards the RFID tag 111 of the ninth embodiment, differences fromthe RFID tag 81 of the sixth embodiment will mainly be described. Indescription of the ninth embodiment, elements having similarconfigurations, operations, and functions to those of the sixthembodiment are designated by the same reference numerals and, in somecases, may not again be described for avoiding duplicate description.

Although in the RFID tag 81 of the sixth embodiment, the first landpattern 6 a and the second land pattern 6 b have been juxtaposed in thewidth direction on the antenna substrate 5, in the RFID tag 111 of theninth embodiment the first land pattern 6 a and the second land pattern6 b are arranged side by side in the longitudinal direction on theantenna substrate 5. The second antenna element 83 b is led from thesecond land pattern 6 b and extends in a meandering manner toward thelongitudinal other end of the antenna substrate 5. The otherconfigurations are substantially the same as those of the RFID tag 1 ofthe first embodiment.

Since the configuration of the ninth embodiment also generates eddycurrent and therefore a magnetic field at the line-to-line capacitancepatterns 85 a and 85 c when receiving a frequency higher than thecommunication frequency, part of the fed electric power is lost as themagnetic field energy. Since the first antenna element 83 a can bedisconnected by increasing the potential difference between theconfronting portions 83 c to eventually cause a discharge, it can beprevented that the entire RFID tag 111 ignites.

Tenth Embodiment

Hereinafter, referring to FIG. 23, description will be given of an RFIDtag 141 that is a wireless communication device of a tenth exemplaryembodiment. FIG. 23 is a plan view showing a configuration of the RFIDtag 141 of the tenth embodiment.

As regards the RFID tag 141 of the tenth embodiment, differences fromthe RFID tag 91 of the seventh embodiment will mainly be described. Indescription of the tenth embodiment, elements having similarconfigurations, operations, and functions to those of the seventhembodiment are designated by the same reference numerals and, in somecases, will not again be described for avoiding duplicate description.

In the RFID tag 141 of the tenth embodiment, a meandering antennapattern 143 is formed so as to meander along the longitudinal directionof the antenna substrate 5 from each of the first land pattern 6 a andthe second land pattern 6 b. For example, the amplitude direction of themeandering antenna pattern 143 is parallel to the width direction of theantenna substrate 5. The antenna pattern 143 includes the meanderingfirst antenna element 83 a and a second antenna element 83 d disposedsubstantially point-symmetrically with the first antenna element 83 aaround the center of the RFID package 2. As long as the second antennaelement 83 d has a meandering shape, the first antenna element 83 a andthe second antenna element 83 d may be line-symmetrical with each other,instead of the point symmetry. The meandering second antenna element 83d having turn portions 83 dc extends from the second land pattern 6 bfinally toward the other end in the longitudinal direction (−Xdirection) on the antenna substrate 5.

The line-to-line capacitance pattern 85 is formed between adjacentrectilinear portions of the first antenna element 83 a. Similar to theseventh embodiment, the line-to-line capacitance pattern 85 includes thethree line-to-line capacitance patterns 85 a, 85 c, and 85 d which areeach arranged alternately depending on the amplitude of the meander ofthe first antenna element 83 a. Similarly, the line-to-line capacitancepattern 85 is formed between adjacent rectilinear portions 83 da of thesecond antenna element 83 d.

The RFID tag 141 of the tenth embodiment is suited to the case ofattachment to nonmetal goods for example. In the case where the articleis a lunchbox for example, due to absence of a metal portion, the RFIDtag 141 having two meandering antenna elements has more improvedcommunication characteristics at the communication frequency, than theRFID tag having the widened portion 7. Even when receiving a higherfrequency than the communication frequency, the RFID tag 141 generateseddy current and therefore a magnetic field at the line-to-linecapacitance patterns 85 a, 85 c, and 85 d, similar to the RFID tag 91,thereby allowing a part of the fed electric power to be lost as themagnetic field energy. Since the first antenna element 83 a can bedisconnected by increasing the potential difference between theconfronting portions 83 c to eventually cause a discharge, it can beprevented that the entire RFID tag 1 ignites.

Eleventh Embodiment

Hereinafter, referring to FIG. 24, description will be given of an RFIDtag 151 that is a wireless communication device of an eleventh exemplaryembodiment. FIG. 24 is an exploded perspective view showing aconfiguration of the RFID tag 151 of the eleventh embodiment.

As regards the RFID tag 151 of the eleventh embodiment, differences fromthe RFID tag 141 of the tenth embodiment will mainly be described. Indescription of the eleventh embodiment, elements having similarconfigurations, operations, and functions to those of the tenthembodiment described above are designated by the same reference numeralsand, in some cases, may not again be described for avoiding duplicatedescription.

Although the antenna substrate 5 of the RFID tag 141 of the tenthembodiment uses the flame-retardant antenna substrate 5 similar to theantenna substrate 5 of the first embodiment, the eleventh embodimentcomprises a normal antenna substrate 153 and a flame-retardant basesubstrate 155, instead of using the flame-retardant antenna substrate 5exemplified in the first embodiment. The base substrate 155 is adheredvia an adhesive such as a double-sided tape to the undersurface of theantenna substrate 153. The other configurations of the antenna pattern143, etc. of the RFID tag 151 of the eleventh embodiment are similar tothe RFID tag 142 of the tenth embodiment.

The antenna substrate 153 is made of PET film for example and may nothave a flame retardance. The thickness of the antenna substrate 153 is38 μm for example. The base substrate 155 has a higher flame retardancethan the antenna substrate 153 and has a flame retardance of the orderof 200° C. in heat resistance. The base substrate is a polyester-basedfilm for example. The thickness of the base substrate 155 is about 25 to50 μm for example.

The line width of the first antenna element 83 a and the second antennaelement 83 d is 125 μm for example. The resistance value of the firstantenna element 83 a from the first land pattern 6 a to the tip is 5Ω to15Ω for example. The second antenna element 83 d also has a similarresistance value. Since the first antenna element 83 a and the secondantenna element 83 d have such a degree of resistance value, whenreceiving a higher frequency than the communication frequency,disconnection is easy to occur at the confronting portions 83 c. Theline width of the line-to-line capacitance patterns 85 a, 85 c, and 85 dis narrower than that of the first and the second antenna elements 83 aand 83 d and is 100 μm for example.

Due to such a configuration, when the RFID tag 151 receives a higherfrequency than the communication frequency, if the energy is large, theantenna pattern is overheated to a high temperature as a result ofreception of the electromagnetic wave energy by the antenna pattern 143.In particular, a high temperature is easy to occur at one or some of theconfronting portions 83 c. A high-temperature part of the antenna bringsabout a minute spark discharge and a part of the antenna pattern 143overheated to a high temperature sublimates, as a result of which theantenna substrate 153 adjacent to the antenna pattern 143 heated to ahigh temperature by the heat also melts out or contracts, making it hardto keep its base shape to consequently disconnect the antenna pattern143. As a result of melting-out or contraction of the peripheral antennasubstrate 153 overheated to a high temperature, the base substrate 155in the vicinity thereof melts out without burning due to its flameretardance. The periphery of the metal conductor of the peripheralantenna pattern 143 inducing a minute spark discharge is coated withthis molten base substrate 155. Accordingly, even though the RFID tag151 generally contracts and curves by the deformation arising from adischarge or heat, the disconnected antenna pattern 143 is enveloped bya part of the molten base substrate 155 as an insulator, whereupon theantenna patterns 143 remain separated from each other, thereby making itpossible to suppress the contact of the antenna patterns 143 with eachother. This can prevent the antenna pattern receiving a higher frequencythan the communication frequency from being reconfigured. The insulationproperties between the wiring of the antenna pattern 143 can also bemaintained.

When there is no base substrate 155, when the antenna substrate 153having no flame retardance melts and contracts around the dischargepoint, the metal conductors making up the antenna pattern 143 maypossibly come into contact with each other. The antenna patternincapable of receiving a higher frequency than the communicationfrequency due to its disconnection results in an antenna pattern of anew pattern by the contact. This enables a higher frequency than thecommunication frequency to again be received, with a risk of furtherdischarge at a part of the new antenna pattern. In this manner, the RFIDtag 151 without the base substrate 155 may have a risk to generate acontinuous discharge.

The RFID tag 151 of the eleventh embodiment can employ an inexpensivefilm for the antenna substrate 153 and can employ an inexpensiveheat-resistant film for the base substrate 155, thus achieving a costreduction. Even though a discharge occurs at a part of the antennapattern 143 and the antenna substrate 153 there around has molten, themolten base substrate 155 envelopes the periphery of the disconnectedantenna pattern 143 so that the disconnected state can be maintained.Accordingly, the antenna pattern 143 cannot again receive a higherfrequency than the communication frequency. Furthermore, by envelopingthe antenna pattern 143 by the molten base substrate 155, it can beprevented, even though the RFID tag 151 deforms due to the heat offusion, that short-circuit is again established to configure a newantenna pattern. It is to be noted that the material of theflame-retardant antenna substrate 5 exemplified in the first embodimentmay be employed for the base substrate 155.

Twelfth Embodiment

Hereinafter, referring to FIG. 25, description will be given of an RFIDtag 161 that is a wireless communication device of a twelfth exemplaryembodiment. FIG. 25 is a plan view showing a configuration of the RFIDtag 161 of the twelfth embodiment.

As regards the RFID tag 161 of the twelfth embodiment, differences fromthe RFID tag 91 of the seventh embodiment will mainly be described. Indescription of the twelfth embodiment, elements having similarconfigurations, operations, and functions to those of the seventhembodiment described above are designated by the same reference numeralsand, in some cases, may not again be described for avoiding duplicatedescription.

When the RFID tag has the widened portion 7 like the RFID tag 161 of thetwelfth embodiment, when attached to an article, it is preferred that anoverlapping region between the article and the RFID tag 161 lies withinthe region of the widened portion 7 (see FIG. 3B). In the RFID tag 161,the antenna pattern 83 is designed assuming the antenna substrate 5 andthe air dielectric constant. Therefore, if the RFID tag 161 is attachedto the article in a manner overlapping with the antenna pattern 83beyond the region of the widened portion 7, the dielectric constant of apart of the antenna pattern 83 differs from the assumed dielectricconstant. This results in formation of a zone shortening the receivedwavelength, thus forming a zone in which the electromagnetic wave energyconcentrates even at a higher frequency than the communicationfrequency.

For example, if the RFID tag 161 is attached to an article with a largedielectric constant such as ceramic in a manner overlapping with theantenna pattern 83 beyond the region of the widened portion 7, thereoccur not only the frequency deviation in the communication frequency ofthe RFID tag 161 but also the concentration of the electromagnetic waveenergy. As a result, the zone overlapping with the dielectric of theRFID tag 161 is subjected to the concentration of overheating by theconcentration of the electromagnetic wave energy, which may cause anignition.

To make clear the position of attachment to goods, the RFID tag 161 ofthe twelfth embodiment comprises a fold portion 165 and a cover portion163 extending opposite to the widened portion 7 in the longitudinaldirection on the antenna substrate 5. The fold portion 165 and the coverportion 163 are integrally formed with the antenna substrate 5. The foldportion 165 has at its outer edges notches 165 a, respectively,extending inward in the width direction. The fold portion 165 has aperforation along the width direction on the antenna substrate 5, withrespective ends of the perforation 167 being connected to the notches165 a. A structure easy to fold such as a V-shaped groove may be formedin place of the perforation 167.

The total length of the circumference or the length of the diagonal ofthe widened portion 7 is designed to be shorter than ¼ wavelength of thewavelength at a specific frequency higher than the communicationfrequency. For example, in the case of the design shorter than ¼wavelength of the wavelength at the frequency of the electromagneticwave heating apparatus (microwave oven), the dimensions of the widenedportion 7 are for example 10 mm in the longitudinal length La and 18 mmin the width-direction length Lb.

Although an end side of the widened portion 7 toward the antenna pattern83 is permitted as the position of attachment to an article, attachmentto the article slightly overlapping with the antenna pattern 83 bringsabout a frequency deviation. Thus, with a safety margin length La2 of 1mm equal to 10% of the length La, the longitudinal length La1 attachedto the article may be remaining 9 mm. A line ML of attachment to anarticle is a straight line extending along the width direction on theantenna substrate 5 at the position of the length La2 from the end sideof the widened portion 7 closer to the antenna pattern 83.

The cover portion 163 is sized such that its end side opposite to thefold portion 165 exactly coincides with the attachment line ML whenfolded along the perforation 167 so as to cover the antenna pattern 83.A double-sided tape is adhered to the entire surface of the RFID tag 161so that when the cover portion 163 is folded along the perforation 167,the cover portion 163 adheres onto the antenna pattern 83.

FIG. 26 is a plan view of the RFID tag 161 with the cover portion 163being folded up along the perforation 167. Since the end side of thecover portion 163 registers exactly with the attachment line ML, theregion of the length La2 of the widened portion 7 is covered with thecover portion 163 while the region of the length La1 of the widenedportion 7 is exposed. As shown in FIG. 27, by adhering the end side ofthe cover portion 163 to an article such as the metal can 14 for examplealong its end portion, the RFID tag 161 can be properly attached to thearticle so as not to cause the frequency deviation.

As described above, the RFID tag 161 may not have the cover portion 163nor the fold portion 165, provided that the RFID tag 161 has on its backside instructions to simply stick the attachment line ML to the articlealong the end portion, with an adhesive being applied to the frontsurface of the RFID tag 161 opposite to the antenna pattern 83 withrespect to the attachment line ML. Instead, symbols such as arrows maybe used to clearly indicate the attachment at the attachment line ML.

Thirteenth Embodiment

Hereinafter, description will be given of an RFID tag 168 that is awireless communication device of a thirteenth exemplary embodiment. Asregards the RFID tag 168 of the thirteenth embodiment, differences fromthe RFID tag 81 of the sixth embodiment will mainly be described. Indescription of the thirteenth embodiment, elements having similarconfigurations, operations, and functions to those of the sixthembodiment described above are designated by the same reference numeralsand, in some cases, may not again be described for avoiding duplicatedescription.

The RFID tag 168 of the thirteenth embodiment differs greatly from theRFID tag 81 of the sixth embodiment in the shape of a meandering antennapattern 169. FIG. 32 is a plan view showing a configuration of the RFIDtag 168 of the thirteenth embodiment. The RFID tag 168 is configured forwireless communication using a high-frequency signal with a UHF-bandcommunication frequency (carrier frequency) and is configured to becapable of wireless communication in a wide frequency band.

The RFID tag 168 of the thirteenth embodiment has a more elongated shapein plan view as compared with the RFID tag 81 of the sixth embodimentand is mounted at its center with the RFIC package 2. That is, theantenna substrate 170 of the RFID tag 168 is of an elongated shape andcomprises an antenna pattern 169 (first antenna element 169 a and secondantenna element 169 b) on both sides of the RFIC package 2 mounted atthe center thereof. The first antenna element 169 a is formed in aregion (right-hand region in FIG. 32) on one hand in the longitudinaldirection on the antenna substrate 170 and extends in a meanderingmanner toward one end in the longitudinal direction. On the other hand,the second antenna element 169 b is formed in a region (left-hand regionin FIG. 32) on the other in the longitudinal direction on the antennasubstrate 170 and extends in a meandering manner toward the other end inthe longitudinal direction.

In the RFID tag 168 of the thirteenth embodiment, a line-to-linecapacitance pattern 171 is disposed to generate a capacitance betweenadjacent turn portions 169 ac and between adjacent turn portions 169 bcin the meandering first antenna element 169 a and second antenna element169 b, respectively. Accordingly, in the RFID tag 168 of the thirteenthembodiment, the turn portions 169 ac and the turn portions 169 bccorrespond to the confronting portions 83 c of the RFID tag 81 of thesixth embodiment. In this manner, in the RFID tag 168 of the thirteenthembodiment, the plurality of LC parallel resonant circuits S are formedalong the respective paths of the first antenna element 169 a and secondantenna element 169 b having an inductance component, these LC parallelresonant circuits S making up the “band elimination filter”. Each LCparallel resonant circuit S in the plurality of LC parallel resonantcircuits S in the thirteenth embodiment is also set so as to resonatewith frequencies in the frequency band of 2.4 to 2.5 GHz used in the“microwave oven”. The line length of each LC parallel resonant circuit Sis set to be shorter than ½ frequency (λ/2) of the frequency band offrequencies (2.4 to 2.5 GHz) of the heating electromagnetic wave.

The RFID tag 168 of the thirteenth embodiment can have a simpleconfiguration like a small tape with narrow width, enabling a low-price,easy-to-handle wireless communication device to be constructed.

FIG. 33 shows a variant of the thirteenth embodiment and is a plan viewshowing a configuration of an RFID tag 172 having the RFIC chip 9mounted on an antenna pattern 173. The RFID tag 172 is configured forwireless communication using a high-frequency signal with a UHF-bandcommunication frequency (carrier frequency) and is configured to becapable of wireless communication in a wide frequency band. The RFID tag172 shown in FIG. 33 has a configuration similar to that of the RFID tag168 shown in FIG. 32 except that the RFIC chip 9 is mounted on theantenna pattern 173 having a loop portion 177. Specifically, an antennasubstrate 174 of the RFID tag 172 is of an elongated shape and comprisesthe antenna pattern 173 (first antenna element 173 a and second antennaelement 173 b) on both sides of the loop portion 177 formed at thecenter of the antenna substrate 174. In the RFID tag 172, a line-to-linecapacitance pattern 175 is disposed to generate a capacitance betweenadjacent turn portions 173 ac and between adjacent turn portions 173 bcin the meandering first antenna element 173 a and second antenna element173 b, respectively. In the RFID tag 172 as well, the plurality of LCparallel resonant circuits S are formed along the respective paths ofthe first antenna element 173 a and second antenna element 173 b havingan inductance component, these LC parallel resonant circuits S making upthe “band elimination filter”.

Each LC parallel resonant circuit S of the plurality of LC parallelresonant circuits S in the RFID tag 172 shown in FIG. 33 is also set soas to resonate with frequencies in the frequency band of 2.4 to 2.5 GHzused in the “microwave oven”, with the line length of each LC parallelresonant circuit S being set to be shorter than ½ frequency (λ/2) of thefrequency band of the heating electromagnetic wave (2.4 to 2.5 GHz).

Thus, the RFID tag 172 shown in FIG. 33, similar to the RFID tag 41, hasa tape-like shape with narrow width, providing an easy-to-handlewireless communication device that is not visually offensive to thepurchaser in the merchandise display.

As described above, the RFID tags 168 and 172 in the thirteenthembodiment provide an easy-to-handle wireless communication device thatdoes not become an obstacle to merchandise display, having a high safetyand reliability because of preventing the risk of ignition in the RFIDtags 168 and 172 even in the case where goods with the RFID tags 168 and172 are dielectrically heated in the electromagnetic wave heatingapparatus (microwave oven).

The RFID tags 168 and 172 described in the thirteenth embodiment havecorner portions of a curved-surface shape for suppressing theconcentration of electric field on the antenna patterns 169 and 173 andthe line-to-line capacitance pattern 171 and 175.

Fourteenth Embodiment

Hereinafter, description will be given of an RFID tag 181 that is awireless communication device of a fourteenth exemplary embodiment. Asregards the RFID tag 181 of the fourteenth embodiment, differences fromthe RFID tag 81 of the sixth embodiment will mainly be described. Indescription of the fourteenth embodiment, elements having similarconfigurations, operations, and functions to those of the sixthembodiment described above are designated by the same reference numeralsand, in some cases, may not again be described for avoiding duplicatedescription.

FIG. 34A is a plan view showing a configuration of the RFID tag 181 ofthe fourteenth embodiment. The RFID tag 181 is configured for wirelesscommunication using a high-frequency signal with an HF-bandcommunication frequency (carrier frequency) and is capable of wirelesscommunication in a wide frequency band. FIG. 34B is a diagram showing,in the form of an equivalent circuit, the configuration of an antennapattern (coil pattern) 183 in the RFID tag 181 of the fourteenthembodiment. As used herein, the HF band refers to a frequency band of 13MHz or more and 15 MHz or less.

As shown in FIG. 34A, the RFID tag 181 comprises an antenna pattern 183having a matching circuit of a loop portion 187 provided with the RFICchip 9 and a capacitor element 182. In the matching circuit of the loopportion 187, the capacitor element 182 is connected at a position facingthe RFIC chip 9. An antenna element 183 a of the antenna pattern 183 inthe RFID tag 181 extends from the loop portion 187 and is formedspirally. The antenna element 183 a shown in FIG. 34A is led in aclockwise inner winding manner from the loop portion 187. A tip as aleading end of the antenna element 183 a is directly connected via abridge pattern 186 to the matching circuit of the loop portion 187. Aninsulating pattern 188 made of a heat-resistant electrically-insulatingmaterial is disposed between the bridge pattern 186 and the antennapattern 183 so as to secure the insulation between the bridge pattern186 and the antenna pattern 183.

In the spiral antenna element 183 a led from the matching circuit of theloop portion 187A, a plurality of line-to-line capacitance patterns 185generating a capacitance between adjacent paths is disposed atpredetermined intervals along the path of the spiral antenna element 183a.

A looped shield pattern 189 is formed inside the antenna element 183 a.The shield pattern 189 is made of a conductive material such as aluminumfoil or copper foil, similar to the antenna pattern 183. The shieldpattern 189 is in the shape of a completely closed loop, but it may be apartly interrupted shield pattern.

As described above, in the RFID tag 181 of the fourteenth embodiment,the plurality of LC parallel resonant circuits S are formed along thepath of the antenna element 183 a having an inductance component, theseLC parallel resonant circuits S making up the “band elimination filter”.Each LC parallel resonant circuit S of the plurality of LC parallelresonant circuits S in the RFID tag 181 is also set so as to resonatewith frequencies in the frequency band of 2.4 to 2.5 GHz used in the“microwave oven”, with line length of each LC parallel resonant circuitS being set to be shorter than ½ frequency (λ/2) of the frequency bandof the heating electromagnetic wave (2.4 to 2.5 GHz).

The RFID tag 181 of the fourteenth embodiment is configured such thatthe antenna pattern 183 and the line-to-line capacitance pattern 185 arelaminated on the surface of the antenna substrate 184. On the surface ofthe antenna substrate 184, the bridge pattern 186 is formed via theinsulating pattern 188 on the antenna pattern 183, to make up theantenna of the RFID tag 181. Thus, the plurality of patterns (183, 185,and 186) are formed on the same surface of the antenna substrate 184,providing a configuration easy to manufacture the RFID tag 181. In theRFID tag 181 of the fourteenth embodiment, the antenna substrate 184 maynot be made of a dielectric, and it may be made of a paper material forexample.

As described in the sixth embodiment referring to FIG. 19C, the RFID tag181 of the fourteenth embodiment also has a circuit configurationcapable of remarkable attenuation for frequencies in the band of heatingfrequency (2.4 to 2.5 GHz) by the “band elimination filter” composed ofthe plurality of LC parallel resonant circuits S. Accordingly, the RFIDtag 181 as a wireless communication device of the fourteenth embodimentis configured to be capable of wireless communication using ahigh-frequency signal having a HF-band communication frequency (carrierfrequency) and is configured to be able to greatly suppress theoccurrence of discharge in the RFID tag 181 even when an article withthe RFID tag 181 is dielectrically heated in the electromagnetic waveheating apparatus (microwave oven), thereby making it possible tosecurely prevent the risk of ignition in the article.

Fifteenth Embodiment

Hereinafter, description will be given of an RFID tag 191 that is awireless communication device of a fifteenth exemplary embodiment. Asregards the RFID tag 191 of the fifteenth embodiment, differences fromthe RFID tag 81 of the sixth embodiment will mainly be described. Indescription of the fifteenth embodiment, elements having similarconfigurations, operations, and functions to those of the sixthembodiment described above are designated by the same reference numeralsand, in some cases, may not again be described for avoiding duplicatedescription.

FIG. 35A is a plan view showing a configuration of the RFID tag 191 ofthe fifteenth embodiment. The RFID tag 191 is configured for wirelesscommunication using a high-frequency signal with an HF-bandcommunication frequency (carrier frequency) and is capable of wirelesscommunication in a wide frequency band. FIG. 35B is a diagram showing,in the form of an equivalent circuit, the configuration of two coilpatterns (193 and 203) including an antenna pattern in the RFID tag 191of the fifteenth embodiment.

As shown in FIG. 35A, the RFID tag 191 of the fifteenth embodimentcomprises a resonant booster circuit having the two coil patterns (193and 203). The coil pattern (primary coil pattern) 203 on one hand of theRFID tag 191 has a matching circuit of a loop portion 200 provided withthe RFIC chip 9 and a capacitor element 202. In the matching circuit ofthe loop portion 200, the RFIC chip 9 is connected at a position facingthe capacitor element 202. The coil pattern (primary coil pattern) 203is led spirally from the loop portion 200, with a tip as a leading endthereof being directly connected via a bridge pattern 204 to thematching circuit of the loop portion 200. The coil pattern (primary coilpattern) 203 is led in a clockwise inner winding manner from the loopportion 200.

The bridge pattern 204 may be formed on the back surface (second mainsurface) of the antenna substrate 194 so that the tip as the leading endof the coil pattern (primary coil pattern) 203 is connected to the loopportion 200 via an interlayer connection conductor extending through theantenna substrate 194. Otherwise, in the case where the bridge pattern204 is formed on the front surface of the antenna substrate 194, aninsulating pattern made of a heat-resistant electrically-insulatingmaterial may be disposed between the bridge pattern 204 and the primarycoil pattern 203 to thereby secure the insulation between the bridgepattern 204 and the primary coil pattern 203.

The antenna pattern 193 as the other coil pattern (secondary coilpattern) in the RFID tag 191 of the fifteenth embodiment is formed so asto surround the coil pattern (primary coil pattern) 203 to configure anantenna element 193 a formed in a clockwise inner winding manner. In thespiral antenna element 193 a of the antenna pattern 193, a plurality ofline-to-line capacitance patterns 195 generating a capacitance betweenthe adjacent paths are disposed at predetermined intervals along thepath of the antenna element 193 a.

The antenna pattern 193 and the line-to-line capacitance pattern 195 inthe RFID tag 191 of the fifteenth embodiment are formed on the frontsurface of the antenna substrate 194. A capacitor element 192 isdisposed on the antenna element 193 a of the antenna pattern 193. Anouter end and an inner end of the spiral antenna element 193 a areelectrically connected directly to each other, via an interlayerconnection conductor 196 extending through the antenna substrate 194, bya conductive path pattern 197 formed on the back surface of the antennasubstrate 194.

A looped shield pattern 199 is formed inside the antenna element 183 a.The shield pattern 199 is made of a conductive material such as aluminumfoil or copper foil, similar to the antenna pattern 193. The shieldpattern 199 is in the shape of a completely closed loop, but it may be apartly interrupted shield pattern.

As described above, in the RFID tag 191 of the fifteenth embodiment, theplurality of LC parallel resonant circuits S are formed along the pathof the antenna element 193 a in the antenna pattern 193 having aninductance component, these LC parallel resonant circuits S making upthe “band elimination filter”. Each LC parallel resonant circuit S ofthe plurality of LC parallel resonant circuits S in the RFID tag 191 isalso set so as to resonate with frequencies in the frequency band of 2.4to 2.5 GHz used in the “microwave oven”. The line length of each LCparallel resonant circuit S is set to be shorter than ½ frequency (λ/2)of the frequency band of the heating electromagnetic wave (2.4 to 2.5GHz).

Thus, the configured RFID tag 191 of the fifteenth embodiment has acircuit configuration capable of remarkable attenuation for frequenciesin the band of heating frequency (2.4 to 2.5 GHz) by the “bandelimination filter” composed of the plurality of LC parallel resonantcircuits S. Accordingly, the RFID tag 191 of the fifteenth embodiment isconfigured to be capable of wireless communication using ahigh-frequency signal having a HF-band communication frequency (carrierfrequency) and is configured to be able to greatly suppress theoccurrence of discharge in the RFID tag 191 even when an article withthe RFID tag 191 is dielectrically heated in the electromagnetic waveheating apparatus (microwave oven), thereby making it possible tosecurely prevent the risk of ignition in the article.

Sixteenth Embodiment

Hereinafter, description will be given of an RFID tag 211 that is awireless communication device of a sixteenth exemplary embodiment. Asregards the RFID tag 211 of the sixteenth embodiment, differences fromthe RFID tag 1 of the first embodiment will mainly be described. Indescription of the sixteenth embodiment, elements having similarconfigurations, operations, and functions to those of the firstembodiment described above are designated by the same reference numeralsand, in some cases, may not again be described for avoiding duplicatedescription.

The RFID tag 211 of the sixteenth embodiment differs from the RFID tag 1of the first embodiment in that a line-to-line capacitance pattern 214acting as a capacitive coupling portion is formed on the same surface(front surface) as the antenna pattern 3, with the other configurationsbeing substantially the same as those of RFID tag 1 of the firstembodiment. FIG. 36 is a plan view showing a configuration of the RFIDtag 211 of the sixteenth embodiment.

The line-to-line capacitance pattern 214 includes first line-to-linecapacitance electrodes 214 a of widened plate shape and secondline-to-line capacitance electrodes 214 b of a narrowed plate shape. Thefirst line-to-line capacitance electrodes 214 a of the widened plateshape capacitively couple specific confronting regions in the meanderingfirst antenna element 3 a to each other and, similarly, capacitivelycouple specific confronting regions 3 ba in the meandering secondantenna element 3 b with each other. The first line-to-line capacitanceelectrodes 214 a are arranged to capacitively couple at least adjacentturn portions 3 ac and adjacent turn portions 3 bc, respectively, in thefirst antenna element 3 a and the second antenna element 3 b,respectively.

On the other hand, the second line-to-line capacitance electrodes 214 bof the narrowed plate shape are disposed to capacitively couple aspecific region of the first antenna element 3 a and a specific regionof the second antenna element 3 b. The second line-to-line capacitanceelectrodes 214 b of the narrowed plate shape are disposed tocapacitively couple the first land pattern 6 a and a specific region ofthe first antenna element 3 a and is disposed to capacitively couple thesecond land pattern 6 b and a specific region (including the widenedportion 7) of the second antenna element 3 b.

The first line-to-line capacitance electrodes 214 a capacitively couplerespective confronting regions 3 aa facing each other in the firstantenna element 3 a, to form a loop circuit composed of the firstline-to-line capacitance electrodes 214 a and a part of the firstantenna element 3 a. This loop circuit is the electric parallel resonantcircuit S. The second line-to-line capacitance electrodes 214 bcapacitively couple respective confronting regions 3 ba facing eachother in the second antenna element 3 b, to form a loop circuit composedof the second line-to-line capacitance electrodes 214 b and a part ofthe second antenna element 3 b. This loop circuit forms the electricparallel resonant circuit S.

Each LC parallel resonant circuit S in the plurality of LC parallelresonant circuits S is set so as to resonate with frequencies in thefrequency band of 2.4 to 2.5 GHz, with the line length of each LCparallel resonant circuit S being set to be shorter than ½ frequency ofthe frequency used as the predetermined communication frequency andfurther to be shorter than ½ wavelength (λ/2) of the frequency band ofthe heating electromagnetic wave (2.4 to 2.5 GHz).

As described above, the RFID tags 211 of the sixteenth embodimentprovides a wireless communication device having a high safety andreliability because of preventing the risk of ignition in the RFID tag211 even in the case where goods with the RFID tags 211 aredielectrically heated in the electromagnetic wave heating apparatus(microwave oven).

The present invention can variously be modified as follows without beinglimited to the above embodiments.

(1) Although in the first exemplary embodiment the confronting regionsof the first antenna element 83 a are rectilinear portions 83 aa, thisis not limitative. For example, if the first antenna element 83 a iscurvilinearly formed, the line-to-line capacitance patterns 85 may bearranged between curved antenna patterns facing each other. Even thoughthe confronting regions of the first antenna element 83 a are therectilinear portions 83 aa, each rectilinear portion 83 aa may not beparallel with the other such that one rectilinear portion 83 aa istilted with respect to the other rectilinear portion 83 aa.

(2) In the conductor patterns such as the antenna pattern and theline-to-line capacitance patterns in the RFID tag of the exemplaryembodiments, their corner portions, etc. are formed from a smooth curvedsurface for suppressing the concentration of electric field.

Although the exemplary embodiments of the present disclosure have beendescribed with a certain degree of detail in the embodiments, it is tobe construed that the contents of disclosure of these embodiments couldnaturally be changed in the details of the configuration and that thecombinations of elements and changes of order in the embodiments couldbe implemented without departing from the scope and thought of theclaimed invention.

The present invention provides a product having a high versatility andusefulness as a wireless communication device attached to merchandiseand especially needed for implementation of “unmanned conveniencestores”.

EXPLANATIONS OF LETTERS OR NUMERALS

-   -   1 RFID tag    -   2 RFIC package    -   3 antenna pattern    -   3 a first antenna element    -   3 b second antenna element    -   4 line-to-line capacitance pattern (capacitive coupling portion)    -   4 a first line-to-line capacitance electrode (widened shape)    -   4 b second line-to-line capacitance electrode (narrowed shape)    -   5 antenna substrate    -   6 land pattern    -   6 a first land pattern    -   6 b second land pattern    -   7 widened portion    -   8 lunch box    -   9 RFIC chip    -   10 inductance element    -   11 external connection terminal    -   11 a first external connection terminal    -   11 b second external connection terminal    -   12 insulating sheet    -   13 through-hole    -   14 metal can    -   81 RFID tag    -   83 antenna pattern    -   83 a first antenna element    -   83 ab extended portion    -   83 b second antenna element    -   83 c confronting portion    -   83 d second antenna element    -   85 line-to-line capacitance pattern    -   85 a line-to-line capacitance pattern    -   85 b line-to-line capacitance pattern    -   85 c line-to-line capacitance pattern    -   85 d line-to-line capacitance pattern    -   87 shield pattern    -   87 a first shield pattern    -   91 RFID tag    -   111 RFID tag    -   141 RFID tag    -   143 antenna pattern    -   151 RFID tag    -   153 antenna substrate    -   155 base substrate    -   161 RFID tag    -   163 cover portion    -   164 antenna substrate    -   165 fold portion    -   165 a notch    -   167 perforation    -   168 RFID tag    -   169 antenna pattern    -   169 a first antenna element    -   169 b second antenna element    -   170 antenna substrate    -   171 line-to-line capacitance pattern    -   172 RFID tag    -   173 antenna pattern    -   173 a antenna element    -   174 antenna substrate    -   175 line-to-line capacitance pattern    -   177 loop portion    -   181 RFID tag    -   182 capacitor element    -   183 antenna pattern    -   183 a antenna element    -   184 antenna substrate    -   185 line-to-line capacitance pattern    -   186 bridge pattern    -   187 loop portion    -   188 insulating pattern    -   189 shield pattern    -   191 RFID tag    -   192 capacitor element    -   193 antenna pattern    -   193 a antenna element    -   194 antenna substrate    -   195 line-to-line capacitance pattern    -   196 interlayer connection conductor    -   197 conductive path pattern    -   198 insulating pattern    -   199 shield pattern    -   200 loop portion    -   202 capacitor element    -   203 coil pattern    -   204 bridge pattern    -   211 RFID tag    -   214 line-to-line capacitance pattern    -   214 a first line-to-line capacitance electrode    -   214 b second line-to-line capacitance electrode

1. A wireless communication device for transmitting/receiving ahigh-frequency signal having a predetermined communication frequency,the wireless communication device comprising: an antenna pattern havingan inductance component; an RFIC element connected electrically to theantenna pattern; and a capacitance pattern configured to capacitivelycouple confronting regions at a plurality of points of the antennapattern that face each other, such that the capacitance pattern andconfronting regions of the antenna pattern form an LC parallel resonantcircuit.
 2. The wireless communication device of claim 1, wherein theantenna pattern comprises a meandering shape having a plurality of turnportions, and wherein the capacitance pattern is configured tocapacitively couple adjacent turn portions of the antenna pattern,respectively.
 3. The wireless communication device of claim 1, whereinthe antenna pattern is disposed on a first surface of an antennasubstrate comprises a dielectric, and wherein the capacitance pattern isdisposed on a second other surface of the antenna substrate that opposesthe first surface.
 4. The wireless communication device of claim 1,wherein the antenna pattern and the capacitance pattern are disposed ona first surface of an antenna substrate, and wherein the capacitancepattern comprises a conductor plate disposed between the respectiveconfronting portions of the antenna pattern that face each other.
 5. Thewireless communication device of claim 4, wherein the antenna patternand the capacitance pattern are laminated via a dielectric on the firstsurface of the antenna substrate.
 6. The wireless communication deviceof claim 1, wherein the LC parallel resonant circuit comprises a linelength that is shorter than ½ wavelength of the predeterminedcommunication frequency.
 7. The wireless communication device of claim6, wherein the line length of the LC parallel resonant circuit isshorter than ½ wavelength of a frequency used in electromagnetic waveheating.
 8. The wireless communication device of claim 1, wherein the LCparallel resonant circuit uses a resonant frequency that is higher thanthe predetermined communication frequency.
 9. The wireless communicationdevice of claim 8, wherein the resonant frequency of the LC parallelresonant circuit is a frequency used in electromagnetic wave heating.10. The wireless communication device of claim 8, wherein the resonantfrequency of the LC parallel resonant circuit is a frequency of a bandof 2.4 to 2.5 GHz that is a frequency band used in electromagnetic waveheating.
 11. The wireless communication device of claim 1, wherein theantenna pattern has a line width that is narrower than a line width ofthe capacitance pattern.
 12. The wireless communication device of claim1, wherein the antenna pattern comprises a meandering shape having aplurality of turn portions, and wherein, in an amplitude direction ofthe meandering shape, a length of the antenna pattern is longer than alength of the capacitance pattern.
 13. The wireless communication deviceof claim 1, further comprising a resin antenna substrate with theantenna pattern formed thereon.
 14. The wireless communication device ofclaim 13, further comprising a film disposed on the resin antennasubstrate, wherein the film has a heat resistance higher than that ofthe resin antenna substrate.
 15. The wireless communication device ofclaim 1, wherein the antenna pattern is configured from a dipole antennahaving two dipole elements, and the capacitance pattern is disposed oneach of the two dipole elements.
 16. The wireless communication deviceof claim 1, wherein the antenna pattern comprises a current path with aleast a portion thereof that forms the LC parallel resonant circuitbeing slimmer than other portions on the current path that do not formthe LC parallel resonant circuit.
 17. The wireless communication deviceof claim 1, wherein the antenna pattern comprises a current path with aleast a portion thereof that forms the LC parallel resonant circuitbeing thinner than other portions on the current path that do not formthe LC parallel resonant circuit.
 18. The wireless communication deviceof claim 1, wherein the antenna pattern is configured for datacommunication using a communication frequency in a UHF band.
 19. Thewireless communication device of claim 1, wherein the antenna pattern isconfigured for data communication using a communication frequency in anHF band.
 20. The wireless communication device of claim 1, wherein theantenna pattern comprises a resonant frequency in the absence of thecapacitance pattern that is higher than the communication frequency.